The U.S. attorney handling the prosecution of a fired Los Alamos scientist accused of mishandling nuclear secrets said today he will resign and turn the Wen Ho Lee case over to a deputy.

John Kelly said his resignation is effective Tuesday. Those familiar with his plans said he is considering a run for Congress.

Asked for additional comment on a statement announcing the move, spokesman Ron Lopez promised Kelly, 52, would have more to say Tuesday.

John Dendahl, who heads the state Republican Party, said he was told Kelly, a Democrat, plans to run for the seat occupied by Rep. Heather A. Wilson (R-N.M.). "I think he ought to keep his day job," Dendahl said.

Democratic state party chairwoman Diane Denish said: "It's my understanding he's looking very seriously at running and will announce his decision shortly."

Kelly's chief deputy for the last six years, Robert Gorence, will be acting U.S. attorney. The Justice Department will announce the appointment of an interim U.S. attorney.

Kelly is in his seventh year as U.S. attorney. He is in the middle of prosecuting Lee for allegedly breaching security at Los Alamos National Laboratory by mishandling nuclear weapons secrets.