WASHINGTON (BLOOMBERG) -Mr Joe Biden will begin his presidency next week with a Cabinet made up mostly of acting officials as delays in the Senate slow confirmation of his top choices for key positions, including the secretaries of defence and treasury.

Senators have set Jan 19, the day before Mr Biden is sworn in, for hearings on his nominees for Homeland Security, Defence, State and Treasury - four key posts that are often targeted for confirmation just hours after a president is sworn in. But they might not be confirmed and able to start work for days or even weeks later.

The House's expected impeachment of President Donald Trump may also affect the Senate's timeline. House Majority Leader Steny Hoyer said late Tuesday (Jan 12) that the impeachment article would be sent over to the Senate quickly, adding a trial to the upper chamber's agenda.

Hearings for Mr Biden's nominees could still proceed, but a Senate trial would take precedence over other floor business in the chamber, potentially delaying their confirmation. Mr Biden said Monday he is talking to lawmakers about a half-day trial timeline.

Mr Biden began announcing his Cabinet nominees shortly after the November election, and introduced each person with a pledge that they would be ready to work on "day one".

But Mr Biden's first day may come and go without confirmations, slowing his promises to gut, reverse or overhaul many of Mr Trump's decisions over the last four years, from the lengthy process of changing regulations to drafting legislation.

Mr Biden can appoint acting heads of agencies while awaiting his nominees to be confirmed. In many cases, he will turn to senior career officials to temporarily lead agencies, a transition official said.

In a few instances, the Biden team has identified Mr Trump's political appointees to take on interim roles, after determining that they share the new administration's values.

Senate-confirmed Democratic members of commissions could take on acting roles leading those agencies until Mr Biden's selections are confirmed, the official said.

The official declined to provide names of any of the people the transition has identified to lead agencies in an acting capacity.

But a person familiar with the matter said Mr Andy Baukol, a long-time civil servant and now a principal deputy assistant Treasury secretary, is likely to become acting Treasury secretary.

Any of those options would put placeholders in critical departments, who are less likely to take the dramatic actions Mr Biden has promised would get under way immediately.

The Senate, which must hold hearings and then vote on each of an incoming administration's nominees, has confirmed some past presidents' nominees hours after their inaugurations.

The setting of hearing dates for Homeland Security nominee Alejandro Mayorkas, Treasury nominee Janet Yellen, State nominee Anthony Blinken and Defence nominee Lloyd Austin suggests the Senate heeded Mr Biden's calls to get critical posts confirmed quickly.

"It's my expectation and hope that the Senate will now move to confirm these nominees promptly and fairly," Mr Biden said Friday of his nominees for those positions.

"I nominated them back in November," he said. "Given what our country has been through the last four years, the last few days, given the threats and the risks in this world, they should be confirmed as close to Jan 20 as possible."

Mr Biden's team continues to make a heavy push on those nominees, particularly Homeland Security, a transition official said. The president's argument is that Mr Mayorkas' confirmation, in particular, would signal the Senate's recognition of threats both from overseas - like the massive cyber attack widely blamed on Russia - and from within the US, like the right-wing mob that attacked the Capitol.

Besides the normal confirmation hearings, Mr Austin also faces a House hearing to waive the rules regarding a former military officer becoming a civilian head of the Defence Department.

On Mr Trump's first day in office, his secretaries of Defence and Homeland Security were confirmed, and his first secretary of State, Rex Tillerson, followed on Feb 1.

President Barack Obama had seven Cabinet choices cleared by the Senate on Inauguration Day, including his Homeland Security chief. His first Defence secretary, Robert Gates, remained in place from the previous administration. His secretary of State, Hillary Clinton, was confirmed on Jan 21.

Former presidents George W. Bush and Bill Clinton had six and three Cabinet members in place on Jan 20, respectively, according to Senate records. Under both presidents, those included Treasury, Defence and State. The Department of Homeland Security was not created until after the 9/11 attacks in 2001.

With Mr Biden's swearing-in only a week away, the coming 50-50 split in the Senate adds complexity. Republicans remain in control of committees until Vice-President-elect Kamala Harris is inaugurated and can break a tie to make Democrat Chuck Schumer the majority leader.

The last time the Senate had split control, in early 2001 under Bush, Senate Republican Leader Trent Lott and Democratic Leader Tom Daschle worked out a power-sharing plan that sped the process. Republican Leader Mitch McConnell and Mr Schumer are using that pact as a framework for their own plan, but the matter is still unresolved, said a person familiar with their deliberations.

After the House's expected vote to impeach Mr Trump over last week's attack on the US Capitol, the Senate must begin a trial that takes precedence over all other business unless all 100 senators agree other business can also be conducted. The chamber, with a simple majority, can also set the rules for a trial and how long it would last.

Impeachment complication

In a half-day Senate trial schedule, the other half would be devoted to Mr Biden's cabinet or other legislation like economic stimulus or money for coronavirus vaccine distribution. Mr Schumer is also exploring whether the Senate could be brought back for an "emergency session" before the Jan 19 end of the current recess to start a trial.

It would be difficult for the Senate to speed Ms Yellen, Mr Mayorkas or Mr Austin into the job on Inauguration Day. That is one day after confirmation hearings, and to move that swiftly would require agreement from every Republican on the relevant committees and the full Senate.

Early partisan jockeying suggests some of the nominations will take more time.

Mr Mayorkas's hearing could be the most contentious, given his work under Obama to fashion the Deferred Action for Childhood Arrivals program, or DACA, which shields from deportation people brought to the US illegally as children. Many Republicans oppose that policy.

As for Mr Austin, the House Armed Services Committee has scheduled a Jan 21 hearing on the waiver he needs because the retired four-star general has been out of uniform for fewer than the required seven years to lead the Defence Department. He also faces some opposition because of his recent work on behalf of Raytheon Technologies Corp, the defence contractor.