President-elect Donald J. Trump’s transition operation announced on Tuesday that it had belatedly signed an agreement with the Justice Department that will allow the F.B.I. to conduct background checks on people Mr. Trump intends to appoint as senior officials in his new administration.

F.B.I. background checks have long been a routine part of transitions. Law-enforcement vetting of a president-elect’s senior team is normally part of decisions about whether they can be entrusted with access to national security secrets, and senators traditionally want to see such dossiers during the confirmation process.

But Mr. Trump, who is hostile to the F.B.I. because of its role in various criminal and counterintelligence investigations into him, had let weeks pass without signing the agreement.

His team considered bypassing the F.B.I. and instead using private investigators. Under that plan, Mr. Trump would grant security clearances to his picks after his inauguration, and the Senate would not have access to the usual vetting materials.

Despite the signing of the agreement, it remains unclear whether Mr. Trump’s team plans to send the names of all officials requiring a security clearance or Senate confirmation to the F.B.I. for vetting. The announcement did not say whether Mr. Trump would require his appointees to undergo the process or was simply allowing the F.B.I. to begin looking at those who are willing to submit to its scrutiny.