It has been three months since Sen. Edward M. Kennedy (D-Mass.) announced he would delay confirmation of Royce C. Lamberth as a federal judge here until Attorney General Edwin Meese III explained why the Reagan administration has picked only white men for federal judgeships in the District of Columbia.

It has been 10 months since Lamberth, a top assistant in the U.S. attorney's office in the District, was nominated to fill the seat vacated more than two years ago when U.S. District Judge Barrington D. Parker took senior judge status. Lamberth's nomination was voted out of the Senate Judiciary Committee by voice vote June 23.

And there is no indication when the Senate Judiciary Committee, now considering the nomination of Judge Robert H. Bork for the Supreme Court, will hear from Meese on his record of selecting candidates for judges here.

Sources said last week that Meese does not seem inclined to explain the administration's record to Kennedy and the committee, and there is no word yet on whether Kennedy might agree to end the standoff by accepting explanations from one of Meese's top officials at the Justice Department.

Kennedy aides maintain that Lamberth, whose nomination is supported by black lawyers' groups, is not the focus of the senator's inquiry. "It's just that 14 white males is an outrageous record," one aide said.

Lamberth, 43, a Texas native who heads the civil division of the U.S. attorney's office, is the first assistant U.S. attorney here ever nominated for a federal judgeship.