The U.S. economy is on track to see strong growth in the coming months, but that can be undone by another surge in COVID-19 cases, Federal Reserve Chairman Jerome Powell said.

In an interview with CBS' "60 Minutes," Powell cautioned against states reopening too quickly and Americans ignoring public health guidelines.

"I'd say that we and a lot of private sector forecasters see strong growth and strong job creation starting right now," Powell said. "So really, the outlook has brightened substantially. And that's the base case. I would say again, though, there really are risks out there. And the principal one just is that we will reopen too quickly, people will too quickly return to their old practices and we'll see another spike in cases."

Despite millions of vaccine doses being administered every day, coronavirus cases are inching northward again in the U.S. The seven-day average for new daily cases as of Saturday was 66,570, up 26% from about three weeks earlier, according to data from the Centers for Disease Control and Prevention. On Friday, the U.S. recorded 81,376 new cases, the most since Feb. 13.

"We do see cases," Powell said. "They're at a much lower level [than in the winter], but we see them moving up now. And that's troubling. It's going to be smart if people can continue to socially distance and wear masks."

One reason the U.S. is positioned for an economic surge, Powell said, is because Congress has passed multiple coronavirus relief packages. The Fed chairman said he'd hate to think of where the country would be today without them. 

"It would've been so much worse," he said.

"This was a very strong economy that was hit by an external force. And tens of millions of people lost their income overnight. ... Congress, in effect, replaced people's income, kept incomes, kept them in their homes, kept them solvent, kept their lives together with what they did in the CARES Act." 

Four relief packages passed by Congress since March 2020 added about $5.5 billion in new spending. At some point, the federal government will need to have a fiscal reckoning, Powell said, adding, though, that now is not the right time.

"The U.S. federal budget is on an unsustainable path, meaning the debt is growing faster than the economy. And that's kind of unsustainable in the long run," Powell said. "That doesn't mean debt is at an unsustainable level today. It's not. We can service the debt we have. We can service the debt we're issuing. And that will remain the case for the foreseeable future. But we'll have to return to a sustainable path. The time to do that is when the economy is strong and we're fully recovered and people are working and taxes are rolling in."