President Joe Biden will announce within days the details of a plan to export 80 million coronavirus vaccine doses to other countries "without any political strings attached," US Secretary of State Antony Blinken said Wednesday.

"In a few short days, in fact possibly as early as tomorrow, the president is going to announce in more detail the plan that he put together to push out 80 million vaccines around the world," Blinken said at the US embassy in San Jose on his last day of a Latin American visit.

"We're going to do that in coordination with Covax... based on science and needs... without any political strings attached," the top US diplomat said, referring to the global vaccine-sharing program.

Biden recently announced a plan to release 20 million more doses over six weeks, bringing the total earmarked for shipping out by the end of June to 80 million.

The boost followed pressure on the Biden administration from other governments to use the United States' large vaccine surplus to help struggling countries, now that significant progress has been made in rolling out vaccinations at home.

The initiative also seeks to address concerns that Moscow and Beijing have been taking advantage of the worldwide crisis to spread influence through distribution of their own inoculations in a so-called "vaccine diplomacy" contest.

Biden has said the move would seek to reclaim "American leadership" in the global fight against the pandemic.

He stressed that Washington was not using the rollout as leverage over countries.