WASHINGTON - The head of Donald Trump’s flagship vaccine project has called on the White House to allow Operation Warp Speed to make contact with Joe Biden’s transition team, warning that interrupting its work would put thousands of lives at risk.

Moncef Slaoui, a veteran pharmaceuticals executive who was appointed by Mr. Trump to accelerate the hunt for a vaccine, told the Financial Times he wanted to make sure his project continued operating without impediment during the transfer of power.

The comments from Mr. Slaoui, whose project is overseeing the development of five potential vaccines, come as the president faces pressure to concede defeat and allow a transition to the Biden administration to begin.

Mr. Slaoui said: “I hope nothing interferes with [Operation Warp Speed]. It is a matter of life and death for thousands of people. The operation has always been about making vaccines and therapeutics available faster for the country and for the world.”

Asked whether that meant allowing the project to make contact with Mr. Biden’s team, he replied: “I would assume, yes.”

However, Mr. Moncef noted that he could not reach out to the Biden team without a green light from the White House. “It's not for us to decide, frankly,” he said.

He added: “We're focused on our objective and we continue the objective. We will deliver the objective, whichever administration asks us to deliver it.”

So far Mr. Trump has refused to allow the General Services Administration to recognize Mr. Biden’s victory in last week’s election—a prerequisite for a formal transition to begin—as the president’s lawyers continue to wage legal battles in swing states around the country.

Pressure is building on Mr. Trump to back down, however, with former national security officials and Republican senators saying this week they want Mr. Biden to receive high-level intelligence briefings.

Mr. Moncef’s intervention comes as the virus continues to spread rampantly in the US, which logged a record 150,526 new cases on Thursday as hospitalizations and deaths continue to climb.

Mr. Trump has been criticized for not doing enough to tackle the pandemic, especially since losing the election last week. He has not met his coronavirus task force for weeks despite the rapid spread of the virus, although on Friday the president announced an afternoon press conference to discuss Operation Warp Speed.