President Joe Biden will announce Tuesday that pharmaceutical company Merck will help manufacture the Covid-19 vaccine from Johnson & Johnson, a senior administrative official who has been confirmed to NBC News.

The announcement comes as the administration works to ramp up production of J & J’s single-shot vaccine. Senior government officials said Sunday the US government will ship J & J’s entire inventory of 3.9 million cans this week, adding that supply would be “uneven” over the following weeks. Another 16 million doses are expected by the end of the month.

Under the agreement, Merck will deploy two facilities in the US for J & J’s vaccine, according to NBC News. One facility produces the vaccine itself, while the other facility provides “fill-finish” services. This is the final stage of the production process when the vaccine is put into vials.

Officials began scouring the country for additional manufacturing capacity after discovering in the early days of government that J&J had been lagging behind in vaccine production, according to NBC News. They soon sought a deal with Merck, which abandoned plans to develop its own Covid-19 vaccine in January after a clinical study showed its shots were ineffective.

J&J declined to comment on the deal with CNBC. In a statement, Merck said it was “unwavering in our commitment to contribute to the global response to the pandemic and prepare us to deal with future pandemics”.

The FDA on Saturday approved J & J’s vaccine for use in people aged 18 and over. Unlike Pfizer and Moderna vaccines, patients with the single dose of J&J do not need to take a second dose and can be stored at refrigerator temperature for months.

In comparison, Pfizer’s vaccine must be stored in ultra-cold freezers that are between minus 112 and minus 76 degrees Fahrenheit. However, the FDA recently allowed the company to store its vaccine for two weeks at temperatures commonly found in pharmaceutical freezers. Moderna vaccine must be shipped at 13 to 5 degrees above zero Fahrenheit.

Earlier this month, White House chief medical officer Dr. Anthony Fauci said he was “disappointed” with the number of cans that J&J was originally expecting, adding that the federal government had assumed there would be “significantly more”.

At the time, Bidens Covid Tsar Jeff Zients said the government was “doing everything we can to work with the company to expedite the delivery schedule”.

This isn’t the first partnership between two drug makers to help improve supplies of Covid-19 vaccines.

In late January, French drug maker Sanofi announced it would help fill and package millions of doses of Pfizer’s two-shot vaccine to meet demand. Moderna has a partnership with the Swiss company Lonza, which makes most of the medicines for the company’s vaccine.

The Biden government has also announced that it is using the Defense Equipment Act to improve supplies of Pfizer’s vaccine.