During his first week in office, President Donald Trump upended U.S. trade policy, directed officials to begin making plans to build a wall on the southern border and ordered an investigation into vote fraud, all with the stroke of a pen.

But experts warn the flurry of activity from the Oval Office could slow to a grind when it comes to the implementation of many of those plans if Trump doesn’t pick up the pace in selecting nominees for hundreds of appointed posts that fill out the executive branch.

“We’re not talking about a small operation here — it’s one of the biggest on the planet,” said Terry Sullivan, the associate director of the White House Transition Project, of the size of the U.S. federal government. “When you don't have people at the helm that means things could run aground.”

More than 1,100 executive branch positions are subject to Senate approval; about 700 of those were deemed crucial by the Washington Post and the Partnership for Public Service. Those include cabinet secretaries, deputy and assistant secretaries, heads of agencies and other management and leadership positions. Trump has so far announced nominees for 33 of the 700 positions; four of those nominees have been confirmed, according to a Washington Post tracker.

It’s a pace that’s only slightly slower than his predecessors, Sullivan said, but “that gap is probably going to continue to widen — and as it widens, that means the government is probably not standing up.”

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That’s because as long as it’s taking to confirm Trump’s cabinet secretaries — at least one, Labor Secretary nominee Andrew Puzder, has had his hearing delayed three times — it’s an even longer road to filling out the rest of the government. That, experts say, typically takes over a year. Lower appointees are subject to the same background check and Office of Government Ethics review as cabinet secretaries, and though their appointments typically win easy confirmation the whole process takes time.

And that clock hasn’t yet started ticking, because the Trump administration hasn’t announced nominees for most of these major appointments. But Sullivan indicated that as long as those key positions remain vacant or filled in the interim by Obama appointees, it will be tough for Trump’s policy shifts to take full effect.

“When you don’t have anybody identified or in place to carry out the administration’s policy, the government continues to do what it was doing,” he said.

The challenge posed by the hundreds of vacancies or Obama Administration holdovers may be even greater for the Trump administration, because many of the president’s cabinet secretaries are business leaders with little government experience.

Max Stier, president and CEO of the Partnership for Public Service, said business experience doesn’t always translate to government, and cabinet secretaries have to be ready to navigate the huge, winding bureaucracy on Day One.

“Large organizations are different in the private sector than they are in the government,” he said. “You don’t have a lot of time for on-the-job learning.”

That’s exacerbated by the loss of institutional knowledge that comes with the exodus of staff from the former administration — a process that’s expected when the White House shifts parties, but one that the Trump Administration has seemed eager to expedite.

On Thursday, the Trump administration ousted four top State Department officials, and news broke that the head of the Border Patrol left a post he had only held since October. That comes the day after Trump announced a raft of new immigration moves, including plans to build a wall on the southern border, that will require full cooperation of the Border Patrol for implementation.

The State Department exodus included the department’s Undersecretary for Management, who had been in the post since 2007, and comes on the heels of the departures of other long-serving diplomats who quit when Trump took over.

State and other federal agencies won’t grind to a halt without key staff; others will take over their positions in the interim. But Stier warned that scenario wasn’t sustainable — and that the consequences could be bigger than Trump’s agenda.

“He’s not going to be able to deal with the crises that will come up as effectively as possible,” he said.

“As much as he may have his own agenda, the world will throw curveballs. It’s hard to do if you don’t have your team in place.”