“We have enough supplies to boost shots, but if Congress doesn’t act, we won’t have the supplies we need this fall,” Biden warned, noting that regulators may approve a fourth shot for all Americans.

Senate Majority Leader Chuck Schumer (D-N.Y.) and Sen. Mitt Romney (R-Utah) have been in talks to revive the COVID-19 package.

If a deal is reached, participants said they expect it to be similar to the bipartisan version of $15.6 billion enacted by congressional leaders earlier this month. The initial compromise fell apart after rank-and-file Democrats opposed cuts to unused pandemic aid to states that could have helped pay for it.

The bipartisan disagreement is on how to save money to offset the cost of the measure, not the new spending itself.

Leaders want Congress to approve the aid before lawmakers take their spring recess after next week.

“We’re not at the finish line yet, but we’re going to keep working throughout the day,” Schumer said Wednesday. Woe to us if a new variant of COVID emerges, he said, “extending its nasty tentacles across the country and we don’t have the tools to deal with it.”

Romney said Tuesday that negotiators are discussing a savings package. “But we are making progress and hopefully we can get there soon,” he said.

A sub-variant of the highly transmissible omicron that scientists call BA.2 is now the predominant coronavirus mutant in the United States. It accounted for nearly 55% of new infections nationwide last week, with a higher rate in the Northeast, according to the latest data from the Centers for Disease Control and Prevention.

One reason BA.2 is making progress, the scientists say, is that it is 30 percent more contagious than the original omicron. In rare cases, studies have shown that omicron can make people sick even if they already have it. But it doesn’t seem to cause any more severe disease than the original, and the vaccine seems to work just as well against it.

However, unvaccinated people are at a much greater risk.