A $600 (£459) jobless benefit paid to tens of millions of unemployed Americans expired overnight after Republicans and Democrats failed to reach a deal on its extension.
Friday was the deadline for an agreement on the coronavirus relief, which tops up state benefits that are mostly far below $600.
Republicans want a smaller relief plan than one passed by the Democrat-controlled House of Representatives.
Talks will continue on Saturday.
The coronavirus crisis has made tens of millions of Americans unemployed, and they have been relying on the $600 payments to cover their bills.
The US economy shrank at a 32.9% annual rate between April and June – the sharpest decline for decades.
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The $600 payments are part of a $2.2tn congressional package adopted in March as coronavirus forced businesses to shut down.
But Congress did not anticipate the current resurgence of the virus, deepening the impact on the economy.
House Speaker Nancy Pelosi, a Democrat, rejected a Republican proposal to extend the benefits for just a week, pending a full agreement.
White House Chief of Staff Mark Meadows said Democrats had rejected reasonable offers, and “what we’re seeing is politics as usual from Democrats”.