In a secure corridor of a government building, officers of a little-known federal police force sit among blinking routers and servers, manipulating and monitoring cameras across the city.

They are officers of the Federal Protective Service (search), which secures more than 9,500 federal buildings nationwide and will play a key role in safeguarding New York and its federal buildings during the Republican National Convention (search).

During an Associated Press reporter's visit this week to its New York control room on the condition that the location not be disclosed, images from cameras flashed across about a dozen flat-panel televisions. The cameras were trained on key security sites in and around the city's federal buildings, capturing video of cars entering parking garages, visitors and employees coming in and out of entrances and pedestrian traffic around building plazas.

In the small, dimly lit control room, officers sitting in front of the screens demonstrated how cameras can zoom in and out to monitor hundreds of locations. The facility, operating 24 hours a day, can take video feeds from as many as 200 cameras and erases footage after 100 days.

"Essentially what we're looking at is one of the better (closed circuit TV) centers there is," said John Ulianko, regional director based in New York.

During the convention, the agency will add 200 uniformed officers trained in crowd control. Many of them, officials said, will be on the streets as cameras watch from above. Some will also be armed with non-lethal guns that can target individuals with plastic pellets filled with paint or tear gas, rather than firing on crowds.

"Our mission is protecting federal buildings," said Ulianko. "The mission doesn't change because there's a big event, or because there are thousands of people on the streets."

But civil liberties advocates have expressed concerns about the surveillance.

"We don't think there is inherently anything wrong with the ability of private individuals and the government to engage in these types of (surveillance) activities," said Udi Ofer, an attorney with the New York Civil Liberties Union. "What we are concerned with is that there is practically no regulation of this activity whatsoever."

Agency officials said they focus their efforts on building security. "This is not an intelligence-gathering operation," said Ulianko.

Following the terrorist strikes on New York and Washington in 2001, protective service officials say they lost some communication capacity in New York. Because of that danger, the agency will move its primary command center during the convention to a mobile unit — essentially a truck that can take camera feeds and coordinate information. The service took the same steps during the Democratic National Convention in Boston.

"With a mobile command center, terrorists cannot shut us down," said Ulianko.