WASHINGTON, DC - The General Services Administration has ascertained that President-elect Joe Biden is the "apparent winner" of the November 3 election. President Donald Trump, who had refused to concede the election, said Monday that he is directing his team to cooperate on the transition but is vowing to keep up the fight.

The move clears the way for the start of the transition of Trump's administration and allows Biden to coordinate with federal agencies on plans for taking over January 20.

An official said administrator Emily Murphy made the determination after Trump's efforts to subvert the vote failed across battleground states, most recently in Michigan, which certified Biden's victory Monday.

"Please know that I came to my decision independently, based on the law and available facts. I was never directly or indirectly pressured by any Executive Branch official -including those who work at the White House or GSA - with regard to the substance or timing of my decision," Murphy wrote in a letter to Biden.

Trump tweeted shortly after her letter was made public: "Our case STRONGLY continues, we will keep up the good ... fight, and I believe we will prevail! Nevertheless, in the best interest of our Country, I am recommending that Emily and her team do what needs to be done with regard to initial protocols, and have told my team to do the same."

Earlier Monday, retiring Tennessee Sen. Lamar Alexander, who has repeatedly called for the transition to begin, released a new statement saying that Trump should "put the country first" and help Biden's administration succeed.

"When you are in public life, people remember the last thing you do," Alexander said.

Republican Sen. Rob Portman of Ohio on Monday called for the head of the General Services Administration to release the 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.

Alexander and Portman, who have both aligned themselves with Trump, joined a growing number of Republican officials who in recent days have urged Trump to begin the transition immediately. Republican Sen. Shelley Moore Capito of West Virginia also urged a smooth transition, saying in a statement Monday that "at some point, the 2020 election must end."

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 Republican 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."

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, 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.