WASHINGTON — Former Senator Joseph I. Lieberman of Connecticut, once President Trump’s preferred candidate for F.B.I. director, has withdrawn his name from consideration, citing his law firm’s central role in Mr. Trump’s legal defense team.

Mr. Lieberman, who has no federal law enforcement experience, said it was a “great honor” to be considered but pulled out after the president tapped Marc E. Kasowitz, a partner in the Manhattan firm that employs Mr. Lieberman, as his counsel in “various” investigations.

“I do believe it would be best to avoid any appearance of conflict of interest, given my role as senior counsel,” Mr. Lieberman, who was Al Gore’s running mate in 2000, wrote in a letter to the White House dated Wednesday and provided by his firm, Kasowitz Benson Torres.