WASHINGTON — President Obama on Friday plans to announce the nomination of James B. Comey, a senior Justice Department official under President George W. Bush, to become the next director of the F.B.I., according to White House officials.

The Senate, which will not be in session in August, is bracing for a significant fight over nominations in July, and it is not clear whether the administration has allotted enough time for the Senate to confirm him by Sept. 3, when Robert S. Mueller III, the F.B.I. director, is mandated to leave his post.

F.B.I. officials in Washington had expressed concern that if Mr. Obama did not nominate a new director by the beginning of June, the bureau would probably have an interim director for some time.

Mr. Comey is best known for his role in a 2004 incident in which, as the acting United States attorney general, he refused to acquiesce to aides to Mr. Bush, who wanted Mr. Comey to reauthorize a controversial National Security Agency surveillance program.