U.S. Office of Management and Budget (OMB) Director Mick Mulvaney (R) listens as U.S. President Donald Trump (L) meets with members of the Republican Study Committee at the White House in Washington, U.S. March 17, 2017. REUTERS/Jonathan Ernst

WASHINGTON (Reuters) - President Donald Trump, who has proposed cuts to an array of government agencies, is asking department heads to offer up plans to operate more efficiently.

Trump’s budget director, Mick Mulvaney, told reporters on Tuesday he would be instructing agencies to outline how they will comply with the president’s budget, which slashed spending for foreign aid and many domestic programs.

The federal hiring freeze imposed shortly after Trump entered office will be lifted on Wednesday, but agencies will be asked to remain mindful of Trump’s goal to reduce the federal workforce, Mulvaney said during a briefing.

Mulvaney acknowledged that the president’s budget would have to be approved by the Republican-controlled Congress, where lawmakers from both parties have balked at some of the drastic reductions.

“One of the reasons this is so difficult to do is you just can’t wave a magic wand in the Oval Office and do these things,” Mulvaney said. “There will be certain things for which we will need legislative authority.”

In the bare bones budget issued last month, the White House did not offer many specific details on how the budget cuts would be achieved.

Mulvaney will ask departments to fill in some of those blanks. Preliminary plans are due from departments in June, with the final versions expected in September.

Not every department gets a cut under Trump’s plan. Mulvaney stressed that some agencies including the Department of Defense and Veterans Affairs department will be able to beef up their workforce.