US President Donald Trump has asked Congress for $7.8bn (£6bn) as an initial payment to help with recovery efforts following flooding in Texas and Louisiana.
Officials say there will be further requests for funds when the full impact of Hurricane Harvey becomes known.
Some residents have been allowed to return to their homes but flood waters are still rising in other areas.
Mr Trump is to visit Texas for a second time on Saturday.
The hurricane made landfall in the state a week ago, causing devastating floods.
It has been blamed for the deaths of at least 47 people and about 43,000 are currently housed in shelters.
In a letter to House of Representatives Speaker Paul Ryan, White House budget director Mick Mulvaney warned that failure to raise the US debt ceiling could hinder recovery efforts.
The debt ceiling is a cap on the total amount the US government can borrow. Only Congress can raise that limit.
“This request is a down-payment on the president’s commitment to help affected states recover from the storm, and future requests will address longer-term rebuilding needs,” Mr Mulvaney said.
Governor of Texas Greg Abbott has said the state may need more than $125bn in aid.