During an appearance before lawmakers on the Senate’s Finance Committee, Treasury Secretary Janet Yellen was repeatedly pressed in often heated terms by Republicans about the lack of a Social Security plan in President Biden’s recent budget proposal.

“Anyone who knows how things get done around here knows it takes presidential leadership to lead major reforms," said Sen. Chuck Grassley (R-IA) on Thursday morning soon after the hearing got underway.

That exchange was soon followed by an intense back and forth with Sen. Bill Cassidy (R-LA) who pressed the Secretary in often personal terms on the president's approach to the issue and claims from Democrats that Republicans seek to cut the program.

“That’s a lie” Cassidy said after Yellen said that Biden stood ready to work with Congress on the issue.

"Why doesn't the president care?" he also asked, noting that he is involved in bipartisan talks on the issue, but hasn’t been able to get an Oval Office meeting to discuss further.

In response, Secretary Yellen offered a defense of her and Biden’s motives, but provided few new details beyond saying that Social Security is a priority for the president and reiterating that the Biden administration would agree to no benefit cuts.

"It's a discussion we need to have," she said.

After the exchange with Cassidy, Finance Committee Chair Ron Wyden (D-OR) jumped in to admionish his colleague and say Cassidy had gone “over the line.” Cassidy responded that he didn’t mean to say Secretary Yellen was lying and that she was only passing along what President Biden has told her.

"Welcome to the Senate Finance Committee Secretary Yellen, we are normally a pretty jovial group," the next questioner, Sen. Tom Carper (D-DE) quipped before moving on to other topics.

Thursday's back and forth comes after another tense exchange on the issue between Sen. Mitt Romney (R-UT) and Shalanda Young, Biden's director of the White House Office of Management and Budget, on Wednesday.

'Not a dime' for Social Security

In the budget itself, Biden opposed cuts to Social Security, but gave no details of new investments in the program beyond a 10% increase in the Social Security Administration's operating budget to do things like improve customer service.

The omission is in striking contrast to Medicare, where the President did offer a detailed plan in his budget that would raise taxes and make other changes to keep the program afloat past 2050.

A recent government trustees report found both programs in peril. Social Security only has the funds to continue paying out 100% of benefits through 2034. After that, benefits could be decreased by over 20%. The report found that Medicare’s key trust fund is in worse shape and will likely run low by 2028 with no action.

The focus on the Medicare plan was a key issue for Cassidy on Thursday. He said that Biden’s plan to increase taxes on Medicare would takes those options off the table for Social Security. He also worried that, when policymakers eventually move to shore up Social Security down the road, a massive ballooning of the national debt could be in the offing if Congress decides to rely on further tax increases to achieve solvency.

Cassidy also took issue with how Biden proposed trillions of dollars in tax increases last week, but "not a dime" going to Social Security.

Yellen was also pressed on the issue by Sen. Ron Johnson (R-WI) who asked about the soaring debt, rhetorically asking of Social Security: "Aren't you concerned about our inability to honor those promises?"

The line of questioning Thursday comes as Social Security becomes a growing issue both in Washington and on the 2024 campaign trail.

Talks are underway across Capitol Hill for how to shore up the program with the most prominent effort led by Sens. Cassidy and Angus King (I-ME). The group is reportedly toying with the controversial idea of raising the retirement age.

The senators recently offered an update on those talks, pledging that with “what we are discussing, millions would immediately receive more, and no one would receive less.” They hope to have “a fully developed plan” that can be released and debated in the months ahead.

Cassidy has also released a bipartisan plan recently to help keep Americans from claiming Social Security too early.

It’s unclear where things go now on talks to shore up the program with Grassley saying Thursday: "It would help a lot if the president would keep demagoguing the Social Security issue the way he has in recent weeks."

Ben Werschkul is Washington correspondent for Yahoo Finance.

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