WASHINGTON — Mayor Bloomberg is wasting no time in lobbying the new Democratic Congress for more homeland security funding for New York.

He will be in Washington today to testify before the Senate Committee on Homeland Security and Governmental Affairs, which is now led by Senator Lieberman, a close ally who won a bitter re-election battle in Connecticut as an independent with a large boost from Mr. Bloomberg.

The mayor yesterday sent a letter to the new majority leader, Senator Reid; the speaker of the House, Nancy Pelosi; the secretary of homeland security, Michael Chertoff; and other federal officials, pushing for Washington to eliminate a restriction that could prevent the city from accessing hundreds of millions of dollars in federal grants to improve emergency communications among municipal agencies.

The city could be barred from the program because it does not use the radio frequency stipulated in a federal law passed last February. While the program provides funds for cities that use a spectrum in the 700-megahertz range, the city has invested more than $1 billion over the last decade in a system in the 400-megahertz range, which corresponds to UHF television channel 16.

New York’s efforts to upgrade its emergency systems have accelerated since the terrorist attacks in 2001, when poor communication among police and fire officials hampered the rescue effort.

Calling the spectrum the city uses “invaluable,” the mayor wrote in his letter that federal security funding should be driven by the particular needs of a locality and that what works for New York might not work as well in other areas. The Federal Communications Commission granted a waiver in 1995 for the city to use the 400-megahertz spectrum.

A spokesman for the mayor, Stuart Loeser, said the city could stand to receive “a couple hundred million dollars” if the restriction is lifted and if the communications grants are distributed based on threat.

A spokesman for Mr. Reid said the majority leader is reviewing the letter, and a spokesman for Ms. Pelosi said it would be passed along to the appropriate committee in the House. The Department of Homeland Security did not respond to repeated requests for comment yesterday.

Mr. Bloomberg’s letter comes less than a week after the city ranked behind 13 other municipalities in a nationwide survey by the Department of Homeland Security of emergency communications in 75 urban and metropolitan areas.

The Senate hearing today will focus on the implementation of recommendations by the September 11 commission, an issue many Democrats campaigned on last year. The House today is expected to pass legislation addressing and implementing many of the recommendations as part the Democrats’ “100-hour” initiative upon taking control of Congress.

The mayor’s appearance in Washington will be the first chance to see if the city’s outlook on homeland security funding has improved now that Democrats are in power, particularly since Mr. Lieberman is in charge of the Senate’s homeland security committee. Mr. Bloomberg campaigned with the senator, who remained in the Democratic caucus, and helped raise funds for his re-election bid.

Mr. Loeser said the mayor was “hopeful” that Mr. Lieberman would be helpful to the city’s concerns. A spokeswoman for the senator, Leslie Phillips, downplayed the importance of their relationship. “I would hope that decisions about homeland security funding to protect the American people have nothing to do with who is friends with whom,” she said.