The Biden administration is planning to purchase 500 million more Pfizer-BioNTech coronavirus vaccine doses to donate to the world, officials said in an op-ed Wednesday.

Why it matters: The move represents a big step toward making the U.S. a major global vaccine supplier just as China has ramped up exports of its Sinopharm, Sinovac and CanSino vaccines, which can be stored at normal refrigerator temperatures.

State of play: The U.S. had already bought 500 million vaccine doses from Pfizer to donate to countries in need.

The country has already donated more than “all other countries in the world combined,” White House coronavirus response coordinator Jeff Zients said during a press briefing last week.