PROVIDENCE, R.I. — Nearly seven years after the attacks of Sept. 11, 2001, the war on terror in this city has evolved into a quiet struggle against a phantom foe.

Last year, when a sailor slipped over the side of a Turkish merchant ship in the city’s port, a Providence police detective assigned to a joint terrorism task force was quickly alerted, reflecting a new vigilance since the Sept. 11 attacks. Alerts also went out to immigration, customs, the F.B.I. and other federal agencies, but the case went cold.

Another alarm was sounded over a suspicious man of Indian descent who asked a metals dealer about buying old power tools and hair dryers. The lead petered out when the prospective buyer told a police detective in an interview that he wanted to refurbish the equipment for resale overseas.

Like most of the country’s more than 18,000 local law enforcement agencies, the Providence Police Department went to war against terror after Sept. 11, embracing a fundamental shift in its national security role. Police officers everywhere had been shaken by disclosures that the police in Oklahoma, Florida, Maryland and Virginia had stopped four of the Sept. 11 hijackers at various times for traffic violations, but had detected nothing amiss.

Over the years since, police officials in Providence joined with state and federal authorities in new information-sharing projects, met with local Muslim leaders and urged their officers to be alert for anything suspicious. Flush with federal domestic-security grants, the police department acquired millions of dollars’ worth of hardware and enrolled officers in training courses to detect and respond to a terrorist attack.

But much has changed. Now, police officials here express doubts about whether the imperative to protect domestic security has blinded federal authorities to other priorities. The department is battling homicides, robberies and gang shootings that the police in a number of cities say are as serious a threat as terrorism.

The Providence police chief, Col. Dean M. Esserman, said the federal government seemed unable to balance antiterror efforts and crime fighting.

“Our nation, that I love, is like a great giant that can deal with a problem when it focuses on it,” said Colonel Esserman, who became chief in 2003 when he was hired by Mayor David N. Cicilline. “But it seems like that giant of a nation is like a Cyclops, with but one eye, that can focus only on one problem at a time.”

“The support we had from the federal government for crime fighting seems like it is being diverted to homeland defense,” he added. “It may be time to reassess, not how to dampen one for the other, but how not to lose support for one as we address the other.”

In Washington, Attorney General Michael B. Mukasey has defended cuts in criminal justice programs. At a Senate Appropriations Committee hearing in April, Mr. Mukasey responded to a chorus of complaints from Democrats. “We’re not pretending that less money is more money,” he said. “But we’re trying to use it as intelligently as we can.”

In a recent interview, Michael Chertoff, the homeland security secretary, cautioned against using domestic security programs to help pay for day-to-day policing needs. “I don’t think we want to take a program designed for one purpose and slowly massage it into another purpose,” Mr. Chertoff said. “If you are pursuing street crime, I don’t think all the organs of national security should be involved in that.”

Some officials of the Department of Homeland Security worry about complacency given the passage of time since Sept. 11 without an attack or concrete evidence of a domestic threat. These officials say they are convinced that Al Qaeda remains determined to strike inside the United States and will find vulnerabilities if vigilance is relaxed.

In Providence, the police have girded for an attack. Flush with money from the Department of Homeland Security, the police bought a 27-foot patrol boat to monitor the city’s port, along with an automated underwater inspection and detection system and a portable small-craft intrusion barrier.

At police headquarters, the department upgraded a video surveillance system, erected 159 concrete posts and 220 feet of guardrails around the building’s perimeter. Supposed targets for attacks, like rail and air terminals, have been inventoried and assessed, and in some cases, hardened against assaults.

The department acquired a small fleet of S.U.V.’s for emergency response, a bomb containment vehicle, a bomb response canine vehicle, mobile data terminals, scuba gear, trauma kits, underwater camera and video gear and special protective suits for all officers. With a $5.6 million grant, it is developing a radio system so police, fire and other emergency responders throughout the region can communicate with one another.

Police officers have enrolled in training that would have been unlikely before Sept. 11. Officers attended a terrorist bombing school in New Mexico, learned how to interpret deceptive responses in interviews, studied unconventional weapons and clandestine explosives laboratories and attended classes in terrorism prevention and suicide bombings.

Today, the boat still patrols the harbor, especially when liquefied natural gas tankers arrive from overseas. The stanchions around police headquarters are in place. The S.U.V.’s, loaded with emergency response gear, have been distributed to field units who use them as part of regular patrols. Most officers have learned to put on and take off their emergency gear, but none of the equipment or training has been needed to respond to a terrorist threat.

From 2002 to this year, the department went from zero to more than $11.6 million in total domestic security grants, according to Police Department figures, while other criminal justice grants, like those from Justice Department programs used to pay overtime and hire more officers, dwindled to less than $4.5 million for the same period.

One Justice Department program, the Byrne Justice Action Grant, which helps the police fight violent crime by paying for overtime and other policing costs, has suffered heavy cutbacks. Providence’s Byrne grant was reduced to $118,000 this year, from $388,000 in 2007.

The Bush administration has proposed eliminating money for the program in its 2009 budget.

Larry Reall, a 21-veteran of the Providence Police Department, is the liaison to the local Joint Terrorism Task Force. He has top-secret security clearance and access to classified computer databases at the local F.B.I. office down the street from City Hall.

In Detective Reall’s six years on the job, none of the hundreds of leads he has chased have turned up a terrorist. But he keeps looking, convinced that his work has made the city safer and may have deterred a potential extremist before a threat materialized. “It’s not whether we are going to be attacked; that’s probably not going to happen,” Detective Reall said. “But I don’t think that you can let your guard down. Just because nothing has happened doesn’t mean that something won’t.”

Police experts said Providence’s experience was similar to that of other cities around the country. Looking back, local law enforcement agencies took on new counterterrorism responsibilities when violent crime rates had plunged to statistical lows.

By 2005 and 2006, while overall crime rates were stable, middle-size and larger cities began to be hit with increases in homicides, robberies and aggravated assaults, said Chuck Wexler, executive director of the Police Executive Research Forum, which studies policing issues.

The International Association of Chiefs of Police recently issued a scathing analysis of federal spending, saying, “Unfortunately, funding federal homeland security efforts at the expense of state, tribal and local law enforcement agencies weakens rather than enhances our nation’s security.”

The frustration is expressed by other Providence police officials. The deputy chief, Cmdr. Paul J. Kennedy, said the department no longer had the flexibility to use federal money to pay for overtime. “I just wish we had some discretion about how we can use this federal money,” Commander Kennedy said. “We know what our problems are. If you say to us the money can only be used for homeland security or equipment, it really limits how effective we can be in fighting crime.”

A weekly meeting of the department’s command staff, in which nearly three dozen city, state and federal officials, including representatives of social welfare and animal control agencies, assemble in a windowless third-floor conference room to discuss crime, focuses heavily on gangs like the West Side Clowns, the Chad Browns and others, mostly associated with crime in the city’s housing projects.

Providence has big-city crime problems, but is small enough so that when the police talk of shootings, assaults and robberies, they sometimes know the victims, the suspects and their families on a first-name basis. Representatives of the F.B.I. and other federal agencies are on hand, but there is little talk about terrorism.

“This is what we do,” Colonel Esserman said of how crime and violence absorbed his department. “We talk about crime. We talk about it all the time. And we try to respond to it as effectively as we know how.”