President Joe Biden has travelled to Texas in his first trip to a disaster zone, visiting workers still reeling from a deadly winter storm.
"You're doing God's work," Mr Biden told emergency workers in Houston.
His visit on Friday came as Texas recovers from a massive energy failure that left millions without electricity amid an unusually severe cold snap.
Dozens of deaths have been blamed on the cold, but it could take months to determine the full tally, US media say.
The energy disaster, which affected some four million residents, came as Texas was seeing the lowest recorded temperatures in more than three decades earlier this month.
Miles of pipes in the south-western state froze and subsequently burst as homes and businesses that are not often insulated against cold weather lost heat.
Water treatment plants also failed, forcing millions of residents to boil water to disinfect it. Thousands collected snow - rare in the state - and used the water to flush their toilets. Several communities are still under orders to boil their water.
Earlier this week, Mr Biden declared a major disaster in Texas, clearing the way for more federal funds to be spent on relief efforts.
Mr Biden's homeland security adviser said on Thursday that $9m (£6.5m) had already been allocated for assistance.
The cold weather that set in over the Valentine's Day weekend has mostly now passed, with temperatures reaching around 78F (26C) in Houston during Mr Biden's visit.
What did Mr Biden say?
In one of his first trips since taking office in January, Mr Biden toured the Houston area with Republican Governor Greg Abbott and First Lady Jill Biden.
Houston - the most populous city in Texas - experienced over one million power outages.
He began by touring the Harris County Emergency Operations Center, where he told workers: "Thank you for what you're doing."
"This is a hell of an operation here," he said, after receiving a briefing from emergency officials.
Harris County at one point had 3.5 million residents without running water, one official told him. Twelve millions bottles of water have since been distributed.
"You're saving people's lives," Mr Biden continued. "As my mother would say, you're doing God's work."
He later visited the Houston Food Bank, the largest food bank in the nation, where he helped pack bagged lunches for school children.
"We're here to help, so put us to work," he told volunteers.
According to reporters travelling with Mr Biden, he packed canned peaches while the governor packed raisins.
He also visited a Covid vaccination centre, run by the Federal Emergency Management Agency (Fema), where he warned that the numbers of infections and hospital admissions could rise again as new variants emerged.
"It's not the time to relax," he said. "We have to keep washing our hands, staying socially distanced and for God's sake wear your mask. It's not a political statement it's the patriotic thing to do."
It is often customary for senators from the affected to state to travel with the president, but the White House said that Covid-mitigation measures allowed for limited space on Air Force One.
Texas Republican Senator Ted Cruz - who was widely mocked for a vacation trip to Mexico amid one of the worst blackouts in US history - delivered a speech on "cancel culture" to a group of conservatives in Florida instead on Friday.
"Orlando is awesome. It's not as nice as Cancun," Mr Cruz said as the crowd laughed. "But it's nice," he added.
The senior Texas Republican senator - John Cornyn - accompanied Mr Biden for the tour. In brief remarks to reporters, the high ranking Republican thanked Mr Biden for issuing an emergency order for the state.
Why did the grid fail in Texas?
Texas lawmakers are holding hearings into the why the state - America's energy capital - was not prepared for the cold weather.
Governor Abbott has blamed the Electric Reliability Council of Texas (Ercot), the grid operator who he says mislead the public about their level of preparations.
A federal report from 2011 advised Texas energy providers to take measures to weatherise infrastructure. But little has been done, beyond filing planning reports.
Officials this week revealed that the grid was only minutes away from total collapse on 15 February. Ercot says that rolling blackouts were necessary to prevent 30 million residents from losing power for months.