Former US presidents Barack Obama, George W. Bush and Bill Clinton are volunteering to take a coronavirus vaccine on camera if it will help promote public confidence.

Obama, in an interview with SiriusXM radio, said he would be inoculated if top US infectious disease expert Anthony Fauci signs off on a Covid-19 vaccine.

"If Anthony Fauci tells me this vaccine is safe, and can vaccinate, you know, immunize you from getting Covid, absolutely, I'm going to take it," Obama said.

"I promise you that when it's been made for people who are less at risk, I will be taking it," he said.

"I may end up taking it on TV or having it filmed, just so that people know that I trust this science, and what I don't trust is getting Covid," Obama said.

Freddy Ford, Bush's chief of staff, told CNN the former president also wanted to help promote vaccination.

"First, the vaccines need to be deemed safe and administered to the priority populations," Ford told CNN.

"Then, President Bush will get in line for his, and will gladly do so on camera."

Angel Urena, Clinton's press secretary, told CNN the former president would also be willing to take a vaccine in public on television

Vaccines developed by Pfizer-BioNTech and Moderna-NIH are expected to be approved by US authorities shortly and a top science official said Wednesday the United States hopes to have immunized 100 million people by the end of February.