US President Joe Biden pledged on Monday that the government would help victims of Hurricane Helene for "as long as it takes," as he dismissed criticism from Donald Trump that he was not in command of the response to the disaster.

"We'll continue to surge resources, including food, water, communications and life saving equipment," Biden said in remarks at the White House, describing Helene as a "history-making" storm.

"We'll be there – as I said before, and I mean it – as long as it takes to finish this job."

Biden also rejected criticism by Republican candidate Trump that he and Vice President Kamala Harris should have been in Washington.

Harris, the Democratic candidate, was on a campaign trip in California while Biden was at his beach house in Delaware and did not return to the White House until Sunday afternoon.

Trump accused Biden at a rally in Pennsylvania on Sunday of "sleeping" instead of dealing with the disaster and said Harris was at fundraisers with her "radical left lunatic donors."

Biden said he would travel to the affected areas across the US southeast "as soon as possible," saying he had been told by responders it would be disruptive to do so immediately.

He added that he spoke with the governors of North Carolina and Georgia as well as officials and leaders in Florida, South Carolina and Tennessee, while also approving emergency requests in seven states.

"I was commanding, I was on the phone for at least two hours yesterday, and the day before as well," Biden said when asked about the criticisms.

"I command, it's called a telephone."

The southeastern United States continues to reel from the deadly storm with over 100 people dead.

Biden said over 600 people remained unaccounted because they could not be contacted but said "God willing they're alive."

Trump will on Monday visit Valdosta, Georgia – where major flooding from the storm occurred.

Georgia and North Carolina are both key states in the tight election being held in just five weeks' time. (AFP)