A partial shutdown of the US government is looming amid a dispute in Congress over provisions in a federal funding bill.
The Senate has blocked legislation passed by the House of Representatives.
The Democrats oppose Republican demands that funding for victims of hurricanes and wildfires be offset with cuts to clean energy programmes.
The BBC reports Congress has to extend funding for the entire government to avoid a partial shutdown on 30 September.
Aid for those hit by Hurricane Irene, Texas wildfires and tornadoes could also dry up by Tuesday if the relief fund is not replenished.
The Senate voted on Friday by 59-36 to block the bill, which was passed overnight in the House by 219-203.
The legislation approved in the House would provide $US3.7 billion of disaster relief. Democrats say that is not enough.
They object to a provision to help pay for it by trimming $US1.5 billion from a programme to develop fuel-efficient vehicles.
The BBC reports this is the same programme that provided more than $US500 million to Solyndra, a bankrupt solar panel maker that has laid off 1100 employees.