WASHINGTON  — Pressure is increasing on President  Trump’s administration to authorize a formal transition process for President-elect Joe Biden as an increasing number of Republicans, national security experts and business leaders say it is time for that process to move forward.

Republican Sen. Rob Portman of Ohio on Monday called for the head of the General Services Administration to release money and staffing needed for the transition. Portman, a senior member of the Senate Homeland Security and Governmental Affairs Committee, also said Biden should receive high-level briefings on national security and the coronavirus vaccine distribution plan.

Sen. Rob Portman, R-Ohio, on Monday called for the head of the General Services Administration to release money and staffing needed for the transition. J. Scott Applewhite/Associated Press, file

Portman, a Trump ally, joined a growing number of Republican officials who in recent days have urged Trump to begin the transition immediately. Sen. Shelley Moore Capito, R-W.Va., also urged a smooth transition, saying in a statement Monday, “at some point, the 2020 election must end.”

Meanwhile, more than 160 business leaders asked GSA chief Emily Murphy to immediately acknowledge Biden as president-elect and begin the transition to a new administration. “Withholding resources and vital information from an incoming administration puts the public and economic health and security of America at risk,” the business letters said in an open letter to Murphy.

Separately, more than 100 Republican former national security officials – including former Homeland Security Director Tom Ridge, former CIA Director Michael Hayden and former Director of National Intelligence John Negroponte – said in a statement that Trump’s refusal to concede and allow for an orderly transition “constitutes a serious threat” to America’s democratic process. The officials signing the letter worked under four presidents, including Trump.

The statement called on “Republican leaders – especially those in Congress – to publicly demand that President Trump cease his anti-democratic assault on the integrity of the presidential election.”

Murphy missed a deadline on Monday set by House Democrats to brief lawmakers about the delay in beginning the transition, which is usually a routine step between the election and the inauguration. A spokeswoman for the GSA said that a deputy administrator would instead hold two separate briefings for House and Senate committees on Nov. 30.

General Services Administration Administrator Emily Murphy Susan Walsh/Associated Press

In response, the Democratic chairs of four committees and subcommittees said they could reschedule the meeting for Tuesday, but no later.

“We cannot wait yet another week to obtain basic information about your refusal to make the ascertainment determination,” the Democrats said in a letter to Murphy. “Every additional day that is wasted is a day that the safety, health, and well-being of the American people is imperiled as the incoming Biden-Harris administration is blocked from fully preparing for the coronavirus pandemic, our nation’s dire economic crisis, and our national security.”

Murphy, who was appointed by Trump, has yet to certify Biden as the winner of the presidential election, stalling the process of officially launching the transition. Trump has publicly refused to accept defeat and has launched a series of court battles across the country making baseless claims of widespread voter fraud and seeking to overturn the election results.

Portman said it was “only prudent” for GSA to begin the transition process immediately.

“Donald Trump is our president until Jan. 20, 2021, but in the likely event that Joe Biden becomes our next president, it is in the national interest that the transition is seamless and that America is ready on Day One of a new administration for the challenges we face,” Portman wrote in an op-ed calling for the transition to begin.

When Murphy ascertains that Biden won, it will free up money for the transition and clear the way for Biden’s team to begin placing transition personnel at federal agencies. Trump administration officials also say they will not give Biden the classified presidential daily briefing on intelligence matters until the GSA makes the ascertainment official.

Among those signing the letter from business leaders were Jon Gray, president of the Blackstone private equity firm; Robert Bakish, president and CEO of ViacomCBS Inc.; Henry Kravis, the co-chief executive of Kohlberg Kravis Roberts & Co., another private equity giant; David Solomon, CEO at Goldman Sachs; and George H. Walker, CEO of the investment firm Neuberger Berman and a second cousin to former President George W. Bush.

The renewed calls for an official transition came as Biden is building out his administration with key picks for national security and foreign policy roles. Former Secretary of State John Kerry will lead the incoming administration’s effort to combat climate change, while Alejandro Mayorkas will be nominated as Homeland Security secretary.

Biden also plans to nominate veteran diplomat Antony Blinken as his secretary of state, according to multiple people familiar with the Biden team’s planning.