WASHINGTON — President Trump went out of his way on Friday to distance himself from Matthew G. Whitaker, his choice to replace Jeff Sessions as attorney general, saying repeatedly that he did not know Mr. Whitaker and had not spoken to him and emphasizing that the new attorney general was merely “there in an acting position.”

“I don’t know Matt Whitaker,” Mr. Trump told reporters as he left Washington for a weekend trip to Paris. But the president stressed that he did know Mr. Whitaker’s reputation well, calling him “a very respected man.”

The faint presidential praise came just two days after Mr. Trump unceremoniously dumped Mr. Sessions, putting Mr. Whitaker in charge of the Justice Department and the special counsel’s investigation into Russian interference in the 2016 election. Since then, criticism has mounted about Mr. Whitaker’s lack of credentials to be the nation’s top law enforcement official, along with allegations that he has conflicts of interest that should keep him from overseeing the Russia inquiry.

Senator Chuck Schumer of New York, the chamber’s top Democrat, sent a letter to Mr. Trump on Friday saying that the appointment of Mr. Whitaker, who was chief of staff to Mr. Sessions, was unconstitutional.