(Bloomberg) -- Debt limit talks in Washington have hit a fresh impasse with negotiators far apart on key issues, especially the spending cuts demanded by Republicans, as time runs short to avert a historic US default.

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Negotiators were tentatively planning to return to the table amid the stalemate. House Speaker Kevin McCarthy said he had spoken to White House negotiators early Wednesday and that discussions would continue. Treasury Secretary Janet Yellen also told a Wall Street Journal forum Wednesday morning that the two sides are still trying to reach a deal.

House Republicans have escalated their accusations that Biden lacks urgency in negotiations, while a Democratic aide called McCarthy unwilling to compromise across a wide spectrum of disputed points, threatening the legislative prospects of a deal.

Republican negotiator Representative Garret Graves said in an interview there was no meeting set and not much progress was being made. But he did not rule out a deal coming together.

“We’re just going to keep working,” he said.

It is not unusual for Congress to strike budget deals at the last minute when the pressure becomes great enough to force negotiators to make painful choices.

Yellen said Wednesday that the world is just seeing the beginnings of the potential market stress if the debt crisis continues.

US stocks are showing increasing signs of concern over the standoff, with the S&P 500 index down 0.8% in early trading Wednesday, after a 1.1% slump on Tuesday. In the Treasuries market, investors are demanding ever-higher premiums on bills that mature when the government is seen most at risk of default. Rates on securities due June 1 and June 6 surpassed 6%.