District and federal law enforcement officials yesterday announced the expansion of Operation Ceasefire, a comprehensive plan to rid the city's streets of illegal guns.

The program emphasizes increased federal firearms prosecutions, a public awareness campaign and community-based violence-prevention strategies. It is a joint effort of the D.C police, the federal Bureau of Alcohol, Tobacco and Firearms, the U.S. attorney's office, the mayor's office and the community.

"Gun violence is costing us plenty," said U.S. Attorney Wilma A. Lewis. "We must put a stop to this senseless violence, and we must do it now."

The expanded project was announced during a 90-minute news conference at the Patricia Roberts Harris Education Center in Southeast Washington, attended by Lewis, Mayor Anthony A. Williams (D), Executive Assistant Police Chief Terrance W. Gainer, ATF Special Agent Patrick D. Hynes, Treasury Undersecretary James Johnson and the family of 7-year-old Dennis Keith Ashton Jr., who was fatally shot two years ago while sitting in his father's car.

The plan has 10 key components, including the creation and staffing of a gang prosecution and intelligence section, increased prosecution of firearms violators and expansion of school- and community-based programs to prevent youth participation in drug trafficking and gun violence.

Hynes, the special agent in charge of the ATF's Washington Field Division, said his agency will work closely with the U.S. attorney's office to identify sources of guns entering the District and augment a task force dedicated to gun crimes. Nearly half of the illegal guns recovered in the District are from Maryland and Virginia, he said.

Operation Ceasefire was launched in 1995 by then-U.S. Attorney Eric H. Holder Jr. The revised version was prompted by President Clinton's directive in March to Attorney General Janet Reno ordering that each U.S. attorney develop a plan to reduce gun violence.

Of the 199 homicides that have occurred in the District so far this year, 157, or 79 percent, were committed with guns, according to police statistics. Nearly 800 aggravated assaults with firearms have occurred this year.

Dennis Ashton Jr., was shot in the head in June 1997 while sitting in a car in a fast-food parking lot with his father and two of his father's friends. Charles Fantroy, 19, of Southeast Washington, pleaded guilty to second-degree murder while armed and was sentenced to 25 years to life in prison. Fantroy said he was shooting at one of the three men in the car.

Fantroy's accomplice, Bernard Coleman, 23, of Southeast Washington, pleaded guilty to manslaughter while armed and carrying a pistol without a license and was sentenced to 16 2/3 years to life in prison.

Meanwhile, Dennis's picture will adorn Operation Ceasefire placards on Metro buses and trains that will read: "Missing Forever. Dennis K. Ashton Jr. Shot dead by a criminal with an illegal gun. Help end the violence. Report illegal guns."