Despite Donald Trump claiming he was not involved in firing a key US attorney believed to be investigating the president and his associates, his top spokeswoman confirmed Monday he signed off on the sacking.

Attorney General William Barr said Saturday that with Mr Trump's approval he had fired Geoffrey Berman as US attorney for Manhattan, a post that saw him oversee the Southern District of New York. The powerful branch of the Justice Department has been investigating a list of things related to Mr Trump, which has reportedly angered the president.

Mr Barr said he had offered Mr Berman a position at Justice Department headquarters and intended to nominate Securities and Exchange Commissioner Jay Clayton to take his place.

White House Press Secretary Kayleigh McEnany on Monday said Mr Berman "decided not to leave" his post in New York, prompting Mr Barr to seek permission to fire him.

"At that point, that's when the president agreed with the attorney general," she said. "He was involved in a sign-off capacity."

That is much more nuanced that what Mr Trump told reporters on Saturday as he left the White House for a campaign rally in Oklahoma.

"Well, that's all up to the Attorney General," Mr Trump said. "Attorney General Barr is working on that. That's his department, not my department. But we have a very capable attorney general. So that's really up to him. I'm not involved."

Even before the Senate had gotten back to work this week, New York's two senators, Minority Leader Chuck Schumer and Kirsten Gillibrand, called on the White House to not even bother formally nominating Mr Clayton.

That's because long-standing Senate protocol allows senators to block nominees for US attorney posts in their home states to which they object. Senate Judiciary Chairman Lindsey Graham, Republican of South Carolina, says he will adhere to the practice.

But Mr Graham, a Trump critic-turned-ally, says the president was within his authorities to remove Mr Berman. Democrats are still howling that he again abused his power.