The White House on Thursday told thousands of political appointees — from ambassadors to schedulers — to resign on Inauguration Day, a formality the Trump administration had stalled for weeks as President Trump disputed the election outcome.

A directive was emailed to agency heads that political appointees must resign effective Jan. 20, the day President-elect Joe Biden takes office, a White House spokesman confirmed. The order was issued by Chris Liddell, the deputy White House chief of staff who has been leading transition arrangements with the Biden team, and was first reported by Politico.

The call for resignations came within hours of Trump’s statement early Thursday that there would be an orderly transfer of power, and as a wave of senior political appointees quit in protest over Wednesday’s storming of the U.S. Capitol by a pro-Trump mob. They include Transportation Secretary Elaine Chao and several senior-level national security officials and press aides.

The White House had refused since the November election to issue the call for resignations, which has been made by every outgoing administration between Election Day and mid-December.

In Trump’s case, White House officials declined to request the resignations because the president refused to acknowledge Biden’s victory, challenging the voting results in the courts, on his Twitter feed and at a rally Wednesday. Congress certified the electoral college results early Thursday.

The administration had sent mixed signals to political appointees across the government in the weeks since Biden’s victory, with the White House personnel director threatening to fire staff who were found to be searching for new jobs.

“What’s unusual about this is not that it was done, but that it was done so late,” said Max Stier, president and chief executive of the nonpartisan Partnership for Public Service, which operates a presidential transition center.

The administration also delayed by about a month issuance of the Plum Book, a listing of political jobs in the government, until a week ago.

The delay in formally notifying the Trump staff to quit has had subtle effects, government experts said. At the State Department, which at 500 has the largest number of political appointees relative to the size of its workforce, foreign governments watched the chaos of the transition and wondered about the fate of ambassadors, a senior U.S. diplomat said.

“They were saying, ‘Are these guys staying or going? It created a lot of uncertainty,’ ” said the diplomat, who spoke on the condition of anonymity to discuss personnel matters.

The delay in formalizing the upcoming departures could have implications, Stier said.

Employees need to meet with their agencies’ personnel staffs to learn about transitioning from their government health insurance plans. Many need to be briefed on ethics rules that govern future contact with their agencies.

It is unclear exactly how many political jobs were filled by the Trump administration. There are approximately 4,000 political appointments available to an incoming president. Trump appointees had the highest turnover of any modern president, and the White House was the slowest at filling senior positions, according to data tracked by the Partnership for Public Service and The Washington Post. Recently, close to 130 Senate-confirmed roles had no nominees.

The government has no ongoing repository that tracks political appointees at lower levels who do not need Senate confirmation.

Biden is likely to appoint career government officials to take on acting senior roles as he waits for Congress to vote on his nominees to lead federal agencies. What’s unknown is whether he will tap any Trump appointees to stay on temporarily to smooth operations until his team comes aboard.

Former president Barack Obama allowed some ambassadors who served in the George W. Bush administration to stay in overseas posts if they had children in school until the school year finished. Trump, when he came into office, fired all Obama-era ambassadors, however.

Jason Briefel, director of policy and outreach for the Senior Executives Association, which represents about 7,000 career and 700 political executives, said it’s possible a new administration would ask a mid- or lower-level political appointee to stay on but that it would be rare in a change of party control.

More commonly, a senior career executive is assigned to step up in a high-level acting role.

“There are protocols for assuring the continuity of government, continuity of leadership,” Briefel said. “As political appointees fall away, it could be that a chief management officer, for example, becomes the acting agency head.” These career executives “are individuals that understand how agencies operate. . . . They are ready, they are prepared.”