Rudy Giuliani tweeted that the Trump campaign has “sued to invalidate hundreds of thousands of fraudulent ballots in the Western District of Michigan”.

“First PA (Pennsylvania), the Michigan will go to Trump,” he tweeted.

“Affidavits will be published tomorrow. You will be shocked.”

Mr Trump’s refusal to concede has prompted senior officials across the government to spread word that any cooperation with Mr Biden’s team is forbidden, officials at agencies and the White House said.

The nation’s top diplomat, Secretary of State Mike Pompeo, refused to accept Mr Biden’s victory as President-elect during remarks at the State Department.

Instead, he said there would be “a smooth transition to a second Trump administration.”

The White House, while offering little formal or explicit guidance, has nonetheless made known throughout the federal government that no steps should be taken that would imply Mr Trump lost the election, according to people familiar with the matter.

“The world should have every confidence that the transition necessary to make sure that the State Department is functional today, successful today and successful with a president who’s in office on January 20 a minute after noon will also be successful,” Mr Pompeo said at a briefing.

The reluctance to begin the formal transition process has prompted increasing concern among Mr Biden’s team, who are mulling legal steps to force the process that would allow them access to federal money and information.

At issue is the official step of “ascertainment,” a formal determination by the General Services Administration that Mr Biden won the election. That would unfreeze more than $6 million (A$8 million) in funding and allow agencies across the federal government – including those responsible for providing highly classified briefings – to begin working with Mr Biden’s teams.

Senior officials at federal agencies have determined their transition plans cannot proceed until that step is taken, according to people familiar with the matter. That means the thick briefing binders prepared by officials before the election are sitting unopened and office space reserved for Mr Biden’s incoming team is dark and vacant while Mr Trump continues to insist his loss isn’t real.

“WE ARE MAKING BIG PROGRESS. RESULTS START TO COME IN NEXT WEEK. MAKE AMERICA GREAT AGAIN!” Trump tweeted on Tuesday.

Mr Trump has made no mention of the steps underway by Mr Biden’s team to launch a transition even as he contests the election results and had been only vaguely aware of the work his administration was doing in preparing for a transition over the past several months, though did have to formally sign off, officials said.

While he did not put up any roadblocks in the planning stages, he was not involved and provided little or no direction.

But privately Mr Trump has taken notice of Mr Biden’s enhanced schedule of presidential-style briefings and speeches, which contrast sharply with his own mostly vacant daily agendas.

Mr Trump made a last-minute appearance in briefing room last Thursday but has otherwise not held an official event in a week.