The D.C. police department hopes to start filling nearly 300 openings for officers with a nine-hour job fair today at the Washington Convention Center.

The gap between the city's authorized police force and the actual number of officers, which stood at slightly more than 3,500 yesterday, has increased. A recent $15 million grant from the U.S. Justice Department to hire 200 additional officers to expand community policing in the District has boosted the city's authorized force to 3,800.

The job fair will take place at the Convention Center, 900 Ninth St. NW, between 8 a.m. and 5 p.m. today, police said.

"We have never held a Career Expo outside of [our] facility," said Bert Ennis, the police department's director of human resources. "This is our first attempt. Hopefully, if we are successful we will do this annually." Police recruiters have regularly gone to military bases, college campuses, high schools and general job fairs, officials said.

Representatives from the department's seven patrol districts, as well as specialized units including the K-9, emergency response, harbor patrol and special investigations divisions, will be on hand to answer questions from applicants and to speak with residents, Ennis said.

Tests for entry-level applicants, usually offered once a month in the District, will be given at 9 a.m., noon and 3 p.m., according to Sgt. Jacob Kishter of the police department's recruiting office.

Chief Charles H. Ramsey plans to deliver two presentations about a new lateral-hiring program that permits the department to hire officers from other law enforcement agencies at salary and seniority levels commensurate with their experience. The new officers can start out earning more than the standard $33,000 annual salary and are eligible to take promotion tests after three years, Ennis said.

The number of openings in the police force is among the highest in recent years, officials said. The department hired 1,500 recruits in 1989 and 1990 but cut corners on background checks and rushed recruits through training to get them on the force. Some of those officers later committed crimes.

Ennis said the department won't repeat those errors. "It is not our intent to compromise at all in terms of background checks," Ennis said. He said the department plans to tighten requirements eventually by implementing a requirement of two years of college enrollment. Current recruits must have a high school or General Educational Development diploma.

In addition, the department is seeking civilians for jobs formerly performed exclusively by officers, including 911 dispatchers, communications operators, personnel recruiters and police aides, said Inspector Jennifer A. Greene, director of recruiting.

Although police departments typically have more candidates than positions, those in big cities such as the District, New York and Philadelphia face a smaller pool of better-educated applicants and feel the effects of the economic boom more strongly, said Dennis J. Kenney, research director at the Police Executive Research Forum, a District-based think tank.

That pressure may only grow stronger. More than 500 D.C. officers now are eligible for retirement. "While we have an aggressive recruitment program this year, it's difficult to keep up with those who are opting to retire," Ennis said.

Metro researcher Bobbye Pratt contributed to this report.