Walgreens Pharmacist Jessica Sahni holds the Pfizer-BioNTech coronavirus disease (COVID-19) vaccine at The New Jewish Home in New York, December 21, 2020.Yuki Iwamura | ReutersThe U.S. government is close to a deal with Pfizer for up to an additional 100 million doses of its coronavirus vaccine, a source told CNBC’s Meg Tirrell on Tuesday.The deal could be announced as early as Wednesday, according to the source. The New York Times first reported the news.Pfizer declined to comment, saying the company “is not able to comment on any confidential discussions that may be taking place with the U.S. government.” The U.S. Department of Health and Human Services did not immediately respond to a request for comment.The news comes after Pfizer CEO Dr. Albert Bourla told CNBC last week that the company was negotiating with the federal government to provide an additional 100 million Covid-19 vaccine doses next year.Pfizer and the U.S. are working out the details on timing, Bourla told CNBC’s “Squawk Box” in an interview on Dec. 14. The company could provide many of those doses in the third quarter of 2021, but the U.S. government is pushing for it in the second quarter, he said.”We are working very collaboratively to try to find a solution and be able to allocate those 100 million [doses] in the second quarter if possible or a lot of them,” Bourla said, adding that the company had not signed an agreement with the U.S. yet.Pfizer already has a deal with the U.S. government to supply 100 million doses of the vaccine as part of Operation Warp Speed, enough to inoculate 50 million people. Under the agreement, Americans will receive the vaccine for free.This is a developing story. Please check back for updates.