It is the deadliest target in a swath of industrial northern New Jersey that terrorism experts call the most dangerous two miles in America: a chemical plant that processes chlorine gas, so close to Manhattan that the Empire State Building seems to rise up behind its storage tanks.

According to federal Environmental Protection Agency records, the plant poses a potentially lethal threat to 12 million people who live within a 14-mile radius.

Yet on a recent Friday afternoon, it remained loosely guarded and accessible. Dozens of trucks and cars drove by within 100 feet of the tanks. A reporter and photographer drove back and forth for five minutes, snapping photos with a camera the size of a large sidearm, then left without being approached.

That chemical plant is just one of dozens of vulnerable sites between Newark Liberty International Airport and Port Elizabeth, which extends two miles to the east. A Congressional study in 2000 by a former Coast Guard commander deemed it the nation's most enticing environment for terrorists, providing a convenient way to cripple the economy by disrupting major portions of the country's rail lines, oil storage tanks and refineries, pipelines, air traffic, communications networks and highway system.

Since 9/11, those concerns have only been magnified. Law enforcement officials have warned of the need to prepare for an assault on one of the four major chemical plants in the area or an attempt to ship nuclear or biological weapons through its two port complexes.

Trying to safeguard more than 100 potential terrorist targets in two miles surrounded by residential communities, industrial areas and commuter corridors has proved a daunting challenge. Federal, state and local officials have spent hundreds of millions of dollars to install gates, roadblocks and security cameras and to provide additional patrols, surveillance and intelligence operations.

But even those in charge of the effort say the job is incomplete, bogged down by obstacles that are a microcosm of the nation's struggle against potential terrorist threats.

After distributing tens of billions to state and local governments since 9/11, the federal Department of Homeland Security cut New Jersey's financing this year to about $60 million from $99 million last year. Many security experts have complained that the formula - which provides Montana with three times as much money per capita as New Jersey - is guided more by politics than by the likelihood of an attack.

Meanwhile, security at Newark Airport, while more rigorous and time-consuming for passengers, has been marred by embarrassing breakdowns, as screeners have repeatedly failed to prevent federal officials from sneaking weapons and fake bombs onto planes.

The time and expense of screening shipping containers has slowed attempts to tighten security at Port Newark and Port Elizabeth, where customs officials say their radiation screening devices are ineffective and need replacement.

The private companies that own 80 percent of the most dangerous targets have given varying degrees of cooperation, officials said, and the chemical industry has effectively blocked attempts in Washington to mandate stricter regulations.

As a result, many of the most crucial security tasks are left to local police departments, some of which say they are too understaffed and poorly equipped to mount a proper counterterrorism effort.

"They tell us to patrol, do this, do that, but don't give us the money or equipment," said Sgt. Michael Cinardo of the Kearny Police Department, one of several law enforcement agencies responsible for patrolling around the chlorine plant.

He said the department requires patrol officers to stop by the plant at least five times each shift.

Security against terrorism is a particularly sensitive issue in New Jersey. More than 700 people killed on 9/11 lived there. And, in October 2001, the first major bioterrorism attack on United States soil was launched from a New Jersey post office when a series of anthrax-laced letters were mailed to members of Congress and the news media. The State Health Department's muddled response came to symbolize the nation's need to prepare itself to face new threats.

Since then, New Jersey officials have spent more than $350 million in state tax money on counterterrorism, building an apparatus that is run by seasoned law enforcement experts and is generally well regarded.

New Jersey's Homeland Security Department, established in 2002, has helped to train, coordinate and increase staffing at local law enforcement and emergency medical agencies; assembled a 1,000-person task force to focus on urban areas; and purchased boats, decontamination suits, radio systems and a computerized intelligence network so federal agents and the New Jersey State Police can share information with all 566 municipalities.

In the most dangerous two miles, they have erected concrete barriers outside hospitals and office buildings and put fences along elevated highways that pass chemical plants. The State Police patrol the skies, highways and coastal waters, and federal officials have used various surveillance techniques. On the New Jersey Turnpike, troopers try to check any vehicle that stops for as little as five minutes.

But given the sheer number of vulnerable sites - three major oil and natural gas pipelines, heavily traveled rail lines and more than a dozen chemical plants - many security experts acknowledge that the response is inadequate.

In the months after 9/11, government officials routinely refused to discuss the most mundane aspects of security, saying that they did not want to offer inside information to potential enemies. Now, said Sidney J. Caspersen, the director of the state's Office of Counterterrorism, there is more risk in remaining silent.

"The terrorists already know what's out here," Mr. Caspersen said. "They have been found with blueprints of our buildings, and a lot of the information is available over the Internet or at a public library. The only question is whether we will find a way to protect these targets before they find a way to attack them."

The answer to that question will depend largely on the ability to operate with limited money and a tangle of bureaucracies.

In several instances, counterterrorism money sent to the state has been used for questionable purposes: the city of Newark spent $300,000 on two air-conditioned garbage trucks, and New Jersey Transit has proposed using $36 million in security money to overhaul the Hoboken Ferry terminal. Even groups like Taxpayers for Common Sense say that places like New Jersey, Houston and Long Beach, Calif., deserve more federal dollars.

As for the ports, the federal Homeland Security Department's inspector general's office recently criticized the agency for directing much of its $517 million in port security money to relatively low-risk sites in places like Kentucky and Tennessee, and not giving enough to busy, vulnerable facilities like Port Newark. Although the Port of New York and New Jersey recently received an additional $42 million for counterterrorism efforts, Port Newark lacks the up-to-date equipment now used to search cargo at ports like Hong Kong.

"We put more resources into securing the average large bank in Manhattan than we do for the entire security of Port Newark," said Stephen Flynn, a former Coast Guard commander who is now a security analyst for the Council on Foreign Relations and who conducted the study that first identified this part of North Jersey as the nation's most terror-prone two miles. "That's just irresponsible."

Some New Jersey officials have hoped that the newly appointed secretary of homeland security, Michael Chertoff, will be sympathetic to the state's situation because he is a native of Elizabeth. But when he visited New Jersey during a terror drill last month, Mr. Chertoff was noncommital about restoring cuts.

"Frankly, it's not a matter of spending a great lot of money," he said. "It's a matter of taking resources we have and having a plan in place so we use them effectively."

New Jersey officials say that the cuts will force them to reduce surveillance of possible targets, cancel training sessions for first responders and counterterrorism experts, and forestall the purchase of equipment to detect chemical, nuclear or biological agents. The state has said it will also have to scale back plans to fortify storage facilities and rail lines near the Pulaski Skyway, an area known as "chemical alley."

Even if New Jersey were to receive more money, however, its counterterrorism effort would still face other difficulties.

At Newark Airport, which handles 32 million passengers a year, the federal government and the Port Authority of New York and New Jersey have spent tens of millions of dollars on high-tech baggage screening equipment, more guards and other security improvements. But Transportation Security Administration employees failed to detect weapons or fake bombs in about a quarter of the 81 tests conducted between last June and September. In December, when a machine detected a simulated explosive, baggage screeners lost track of it and it was loaded onto a flight to Holland.

Meanwhile, even less has been done to secure the nation's greatest vulnerability to terror attacks, its 15,000 chemical plants, 123 of which pose a threat to at least 1 million people, according to the Environmental Protection Agency. A spokeswoman for the Chemistry Council, an industry group representing 150 of the nation's largest chemical plants, said its members had already invested $2 billion in improved security and were working with Congress to establish federal safety guidelines.

"We want to work with the Department of Homeland Security and Congress to make these plants safer in a way that works for everyone," Kate McGloon, the spokeswoman, said.

Michelle Petrovich, a Department of Homeland Security spokeswoman, said agency officials had visited more than half the nation's 300 most dangerous plants and urged the companies to enhance perimeter security and switch to less hazardous chemicals and processes. As a result, Ms. Petrovich said, she believes North Jersey is "one of the safer areas because it has received the most attention in terms of protective measures."

But Richard A. Falkenrath, a former deputy homeland security adviser to the White House, said that effort has done little to make the public safer. "Saying that you're doing something doesn't mean you're actually making a difference," said Mr. Falkenrath, who recently testified before Congress, urging tighter regulation of the chemical industry.

Since 2001, at least two major efforts to bolster chemical plant security have been stalled, in part by industry lobbyists.

The latest proposal to tighten security at chemical plants, which appears to be gaining support in Congress, would establish safety guidelines. But Senator Jon S. Corzine said that it is only a half measure because it would not mandate that plants in densely populated areas stop using highly dangerous chemicals like chlorine gas and switch to more benign alternatives, like sodium hypochlorite. The plants use such chemicals to make antiseptics for water purification plants.

For those who live in the shadow of these plants, there is little expectation that the federal government will mount a more vigorous security response.

Carolyn M. Chapluske of Kearny, who has lived in North Jersey all her life, said, "People pay taxes and deserve to be protected. But they probably won't. It's just the way things work."