WASHINGTON (AP) – Mayor Bloomberg urged Congress on Monday to scrap a rule on emergency radio transmissions that he argues hurts his city, which has invested millions of dollars in upgrading police and fire communications since the 2001 terror attacks.

Mayor Bloomberg was due to testify before a Senate panel about the issue of emergency communications on Tuesday, a week after a federal report gave the city good – but not great – grades on its emergency radio systems.

Ahead of the hearing on implementing the recommendations of the 9/11 Commission, Mayor Bloomberg sent a letter Monday to new Democratic Majority Leader Harry Reid, arguing that Congress cut his city out of a $1 billion fund for upgrading emergency radio systems.

“I am deeply concerned about an apparent grant restriction that could effectively preclude the city’s public safety agencies from using these grants to improve the quality and extent of communications interoperability in New York City,” Mayor Bloomberg wrote to Senator Reid.

Since Sept. 11, when New York’s radio system was overwhelmed and some firefighters did not receive critical radio messages, interoperability has become a buzz word among state and local authorities and the federal agencies that pay for radio improvements.

At issue is what frequency state-of-the-art police and fire radios should use. A $1 billion federal fund is aimed at cities that use spectrums in the 700s megahertz range, while New York has spent years building up its system in the 400s range, which corresponds to the UHF television channel 16 frequency.

The technological standoff between the city and Congress comes as the new Democratic majority is pushing for implementation of outstanding recommendations from the now-defunct 9/11 Commission, among them improved emergency radio systems and more money for big cities’ anti-terror programs.

Mayor Bloomberg, in his letter, argued Congress should change the law to help fund his city’s 400 MHz range improvements, since the Federal Communications Commission in 1995 gave the city a waiver to use the UHF channel 16 spectrum, which the mayor said “works well for New York City given its unique size, density and in-building and underground coverage needs.”

Experts say signals in the 400 MHz range tend to travel farther and penetrate deeper through structures than the higher 700 MHz range, a major issue in a city of towering skyscrapers and underground subway tunnels.

Mayor Bloomberg argued that if the requirement stays on the books, the city may have to spend even more money to switch again to the 700 MHz range.

A spokesman for the Department of Homeland Security did not immediately return a telephone message seeking comment Monday.

Last week, a federal scorecard of 75 U.S. cities and urban areas found New York had well-developed, but not the most advanced, emergency communications systems. Six other cities received the highest possible grades, and a total of 13 scored better marks than New York.