Donald Trump announced that his budget director Mick Mulvaney will step in as acting chief of staff to replace John Kelly-amid indications the president is struggling to fill the key post.

Trump, whose presidency is increasingly embroiled in legal troubles, announced earlier this month that Kelly, a former Marine Corps general, was leaving. Kelly, who reportedly fell out with other close "Mick has done an outstanding job while in the Administration," Trump said on Twitter. "I look forward to working with him."