President Joe Biden will announce a major partnership Tuesday afternoon between pharmaceutical giants Merck & Co. and Johnson & Johnson to help produce J&J’s newly authorized vaccine.

“The US Government will facilitate this partnership in several key ways including invoking the Defense Production Act to equip two Merck facilities to the standards necessary to safely manufacture the vaccine and asking the Department of Defense to provide daily logistical support to strengthen Johnson & Johnson’s efforts,” White House press secretary Jen Psaki said on Tuesday afternoon.

The move could help increase supply of the single-shot vaccine. Biden is expected to elaborate on the rivals teaming up with remarks in the State Dining room at 4:15pm ET.

The U.S. Food and Drug Administration approved an Emergency Use Authorization for the J&J vaccine Saturday, which triggered the shipment of 3.9 million doses of the vaccine on Monday. Of those, 800,000 are expected to go directly to pharmacies. The first shots were being administered Tuesday.

J&J had originally estimated it could ship 12 million doses at the end of February in a $1 billion contract signed with the federal government in August.

Despite the low initial availability, Johnson & Johnson CEO Alex Gorsky said the company expects 20 million doses to be available by the end of March and to meet its contractual obligation for 100 million doses by the end of June. He also said Johnson & Johnson is expected to produce almost 1 billion doses by the end of the year.

Psaki says that the partnership “should” help Americans get the shots sooner.

“It definitely will expedite the efforts of the United States government, having enough vaccines on hand to vaccinate the American public,” Psaki said to ABC News Senior White House Correspondent Mary Bruce.

J&J declined to comment on whether the new partnership would impact its timeline to deliver vaccines in the U.S.

Merck also declined to provide details, with a spokesperson saying only that the company “remains steadfast in our commitment to contribute to the global response to the pandemic and to preparing to address future pandemics.”

The J&J vaccine on Saturday became the third FDA authorized COVID-19 vaccine, joining Pfizer and Moderna. However, those other vaccines require two doses for full immunization. The J&J vaccine is not only administered as a single dose but is also easier to store, only requiring regular refrigeration.

The J&J vaccine also differs from its competitors in that clinical trials were conducted in Latin America and South Africa and tested against different COVID-19 variants.

“About 40% of the patients in the trial were in Latin America,” Gorsky said on Good Morning America on Monday. “We had about another 15% in South Africa. In South Africa over 90% of those patients were infected with the South African strain.

Gorsky said the vaccine is 100% effective against hospitalizations and deaths.

Biden administration officials are urging Americans to get vaccinated to help control the coronavirus pandemic and advising people to take any vaccine that is offered.

“All of these vaccines are safe. They are effective. They’ve been approved by the FDA,” White House press secretary Jen Psaki said on Monday.

The country’s leading infectious-disease expert, Dr. Anthony Fauci, is also stressing that Americans should take whatever vaccine is provided to them, saying he would do the same.

“I’m vaccinated now,” he said on ABC News’ “This Week” with George Stephanopolous. But if I were not vaccinated, and I was going to go into a clinic, and they said, ‘hey, we have J&J now, or you can wait three weeks or so to get another one,’ I would take the one that is available to me now, because the quicker you get vaccinated, the more quickly you will be protected, and you will add on to the overall protection in your county, in your country.”

ABC News’ Anne Flaherty contributed to this report