By THOMAS J. LUECK A $6 million federal grant has been awarded to expand an emergency response radio network used by police officers, firefighters and other city workers to their counterparts in several suburban counties, Mayor Michael R. Bloomberg said yesterday. The Department of Justice grant is intended to broaden the existing UHF analog radio network, developed largely after the 2001 attack on the World Trade Center revealed serious gaps in the ability of the police and firefighters to communicate during an emergency. City officials said the $6 million would pay for radio signal repeaters. These would extend communications from first responders in the city to those in Westchester and Nassau Counties and parts of Suffolk County in New York, and in Bergen, Hudson and Essex Counties and parts of Passaic County in New Jersey. “Regional communication among first responders is critical to managing a large-scale crisis,” Mr. Bloomberg said in a joint statement with other city officials. He said the federal grant would “establish a robust radio system” linking the Police and Fire Departments and Office of Emergency Management with their sister agencies. Police Commissioner Raymond W. Kelly said, “This grant recognizes the fact that disasters don’t respect boundaries, and that we need to communicate beyond them.” The effectiveness of emergency radio communications has drawn scrutiny since 9/11, in part because lives were lost that many officials say could have been saved with better communication. In a report issued in April, the federal National Institute of Standards and Technology found that poor communication “likely contributed to the loss of emergency responder lives.” The city’s radio network has six emergency response channels, three of which are to be made accessible to emergency responders in the suburban counties, city officials said. The grant “will allow us to continue to build the most robust interoperable radio system anywhere in the country,” said Joseph F. Bruno, the city’s commissioner of emergency management. Fire Commissioner Nicholas Scoppetta said, “One of the lessons we learned four years ago was the need for a regional approach in addressing large-scale disasters.”