Watch live: Trump officials to announce expansion of Covid vaccination eligibility

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Officials from the Health and Human Services Department and Pentagon are holding a joint briefing Tuesday on the Trump administration's Covid-19 vaccine program Operation Warp Speed.

The administration plans to issue new guidelines to expand vaccine eligibility to everyone 65 and older as well as to those with comorbid conditions, like diabetes, a senior official told CNBC earlier Tuesday.

The administration will also stop holding back millions of doses reserved for the second round of shots of Pfizer and Moderna's two-dose vaccines, the official said, adding they released doses that had been held in reserve on Sunday.

U.S. officials are trying to pick up the pace of vaccinations after a slower-than-expected rollout. As of Monday morning, more than 25.4 million doses had been distributed across the U.S., but just over 8.9 million shots have been administered, according to CDC data.

Read CNBC's live updates to see the latest news on the Covid-19 outbreak.