President-elect Joe Biden will appoint interim agency heads to lead Cabinet agencies and departments while his nominees await confirmation, a necessary move because of delays in the transition process, a Biden transition official said.

Biden, a Democrat, will be inaugurated on Jan. 20, taking over from Republican President Donald Trump, who is leaving amid an impeachment process related to the deadly Capitol riot last week.

Trump’s administration delayed the process of transferring power while he claimed, falsely, that the election results were fraudulent.

The transition official said the delay had put the process far enough behind that Biden would have to make temporary appointments to lead the government’s key agencies, while political appointees such as chiefs of staff could start enacting his agenda.

The official said Biden’s team had identified career officials, including some from Trump’s administration, whom he described as people of integrity that Biden would put in place until the confirmation process concluded.

More than 300 former U.S. ambassadors issued a statement on Tuesday calling for the Senate to swiftly confirm Biden’s choices for secretary of state, Antony Blinken, and ambassador to the United Nations, Linda Thomas-Greenfield.

“They are crisis-tested experts who will renew American leadership, rebuild our alliances and partnerships, and restore our credibility on the world’s stage,” the former envoys, including Thomas Pickering, Caroline Kennedy and Michael McFaul, said in the statement.

The Wall Street Journal first reported the president-elect planned to make temporary appointments to lead most cabinet and some sub-Cabinet positions.

The U.S. federal agency that signed off on the presidential transition process told Biden on Nov. 23 that he could formally begin the hand-over process. The election took place on Nov. 3, and Biden was declared the winner on Nov. 7.

Biden, a former vice president, has said that some Trump administration officials were dragging their feet in sharing information.

The impeachment process adds a wrinkle. If the U.S. Senate is in the middle of an impeachment trial against Trump at the begin