Updated at 3:30 p.m. ET

Speaking at a White House coronavirus vaccine summit Tuesday, President Trump praised his administration for fast-tracking vaccines and boastfully criticized those who he said had doubted his ability to oversee a vaccine production.

Calling vaccine development a "a monumental national achievement," Trump said the collaboration of government, scientists and industry will save millions of lives around the world.

"It will end the pandemic," he said.

He also signed an executive order that will prioritize Americans' access to the vaccine. His administration has said it has a plan in place to get doses to 300 million Americans within six months.

Trump also continued to push mistruths about the outcome of the presidential election. When asked why the White House had not extended an invitation to those working with President-elect Joe Biden, whose administration will need to implement mass vaccine distribution, Trump deflected and again raised the false claim that a true victor had not yet emerged in the race.

"We're going to have to see who the next administration is," Trump said.

He called on state legislatures and courts to "have the courage to do what everybody in this country knows is right," falsely accusing Biden of having won because of widespread voter fraud.

In his remarks to reporters, Trump also repeated that the number of cases of the coronavirus in the United States is high because of the amount of testing done in the U.S. — which is not true — and defended his decision to hold Christmas parties inside the White House, saying there were smaller guest lists than usual and that many guests wear masks.

The White House's "Operation Warp Speed" summit — which includes public health experts, business leaders and state legislators — comes as lawmakers and pharmaceutical companies prepare for the rollout of a coronavirus vaccine.

The Trump administration viewed the event both as an opportunity to outline how it will kick-start the widespread distribution of a vaccine and as a chance for the president to highlight the way his administration has contributed to the rapidly developed vaccines.

Representatives from the drug manufacturing companies Pfizer and Moderna, the two leading contenders for a coronavirus vaccine, did not attend the event. But executives from FedEx and UPS, both of which are expected to help distribute the vaccine across the country, were listed among the attendees.

The Food and Drug Administration is preparing for a gathering of its own this week to assess whether to grant emergency use authorization to a vaccine developed by Pfizer. On Tuesday morning, the FDA released an analysis that found the vaccine to be effective and safe.

Also on Tuesday, the United Kingdom kicked off its nationwide coronavirus immunization campaign.

The White House summit overlapped with an event hosted by Biden, who formally introduced his health care team on Tuesday afternoon.

Dr. Anthony Fauci, one of the most public-facing officials in the fight against the virus, was invited to attend the White House summit but was unable to because of a "scheduling conflict," the officials said.

Fauci, who has been tapped to serve as Biden's chief medical adviser, virtually attended the Biden event.

"I hope that you don't mind that the reason that I am sending this video is because a close friend and colleague at the NIH, Dr. Harvey Alter, is receiving the Nobel Prize in medicine at the same time and we wanted to attend the ceremony at the NIH to show our support," Fauci said.

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