President Donald Trump has essentially given "Operation Warp Speed" a blank check as the team of government officials, scientists and private companies aims to produce hundreds of millions of doses of a life-saving coronavirus vaccine by early next year.

The goal — which may prove impossible to meet — is to make 100 million doses of the vaccine available by November, 200 million doses by December and 300 million doses by January, a senior administration official said.

"When the President was asked, 'What do you want to put into it?' He said, 'No limit,'" the official said.

Trump insisted Thursday the administration wasn't "overpromising" with its aggressive timeline.

"Whatever you can humanly do, we're going to have," Trump said. "We're going to fast-track it like you've never seen before, if we come up with a vaccine."