Later, President Donald Trump said that he would raise his offer for a stimulus package above his current level of $1.8 trillion. House Democrats have passed a $2.2 trillion bill.
"I would. Absolutely I would. I would say more. I would go higher. Go big or go home, I said it yesterday," the president told Fox Business.
"Nancy Pelosi doesn't want to give anything. She thinks it helps her with the election," Trump continued. "And I don't think so. I think it hurts her with the election because everyone knows she's holding it up. We're not holding it up. She's holding it up."
The president also took a swipe at his Treasury secretary, "So far he hasn't come home with the bacon."
House Speaker Nancy Pelosi, the lead negotiator for Democrats, had identified testing as one of the main sticking points in talks. Mnuchin appeared to cede ground to the speaker in an interview on CNBC's "Squawk Box."
"That issue is getting overblown," Mnuchin said. "We've agreed to $178 billion overall for health. It's an extraordinary amount of money. We'd agreed with the Democrats with $75 billion going to testing, contact tracing."
"What we have been focused on is the language around testing," he added. "When I speak to Pelosi today, I'm going to tell her that we're not going to let the testing issue stand in the way. We'll fundamentally agree with their testing language subject to some minor issues. This issue is being overblown."
Pelosi, whose party passed a $2.2 trillion relief bill in the House, has criticized the White House's latest $1.8 trillion proposal as insufficient.
But the conciliatory comments from the White House met resistance from Senate Majority Leader Mitch McConnell later in the day. The Kentucky Republican rejected the idea of a coronavirus relief package larger than $1.8 trillion and deemed his own $500 billion plan a more appropriate response.
"My members think what we laid out – a half a trillion dollars, highly targeted – is the best way to go. So that's what I'm going to put on the floor," McConnell said. "It's what Senate Republicans ... feel like is an appropriate response."
The mixed signals from the nation's top Republicans came after the Labor Department's jobless claims report added to concerns that the recovery in the U.S. labor market may be slowing.
The department reported that the number of first-time applicants for state unemployment insurance rose to 898,000 during the week ended Oct. 10. That total was the highest number since Aug. 22.
The public health crisis also shows few signs of abating, adding urgency to calls for further federal intervention.
Daily new U.S. cases of the coronavirus, as a seven-day average, continued to rise and topped 52,345 as of Wednesday, according to a CNBC analysis of Johns Hopkins data. Average daily new infections are 17% higher than a week ago and have been growing for the last 10 days.
Negotiations between the White House and Congress have been deadlocked for weeks, but the prospects for a deal before the 2020 election appeared to dim on Wednesday after a spokesman for Pelosi highlighted testing as a key difference between the two sides.
"One major area of disagreement continues to be that the White House lacks an understanding of the need for a national strategic testing plan," spokesman Drew Hammill wrote on Twitter. "The Speaker believes we must reopen our economy & schools safely & soon, & scientists agree we must have a strategic testing plan."
The comments from the Treasury secretary and the speaker earlier in the week weighed on equities on Wednesday, when the Dow lost 160 points and the S&P 500 shed 0.7%. U.S. stocks appeared set for their third straight day of losses Thursday morning as the Dow dropped 275 points and the S&P 500 lost 1.1%
Trump said he had scrapped stimulus talks earlier this month until after the election, but he later reversed course and called for a big relief package as his Democratic challenger, Joe Biden, extended his lead in national polls.