(WASHINGTON) — When President Joe Biden unveiled his $6.8 trillion budget proposal for fiscal year 2024 on Thursday, notably absent was a plan to shore up the finances of Social Security.

Biden’s placed an outsized emphasis on Social Security and Medicare since clashing with Republicans over the programs in his State of the Union address last month. He’s repeatedly hammered the GOP over the issue, accusing some members of wanting to target benefits as Congress gears up for a battle over the debt ceiling and federal spending.

“I guarantee you I will protect Social Security and Medicare without any change. Guaranteed. I won’t allow it to be gutted or eliminated, as MAGA Republicans have threatened to do,” Biden said to applause as he rolled out his plan in a campaign-style speech to a union crowd in Philadelphia.

The 184-page budget reiterates Biden’s position that cuts to Social Security are off the table, and includes an additional $1.4 billion for the Social Security Administration to improve customer service.

But while the proposal addresses Medicare’s solvency, it doesn’t include a similar plan for Social Security — which could see a reduction in scheduled benefits by roughly 20% starting in 2034 unless lawmakers take action.

For Medicare, which is on track to deplete its trust fund in 2028, Biden’s proposed tax increases on the wealthy and bringing down drug costs would bolster the program’s finances through 2050. The plan was unveiled by Biden in an op-ed for the New York Times two days before the official budget release.

The nonpartisan Committee for a Responsible Federal Budget, responding to Biden’s proposal, praised the Medicare measures but said it was “extremely disappointed it neglects Social Security, putting seniors’ benefits at risk.”

Andrew Biggs, a senior fellow at the conservative-leaning American Enterprise Institute, told ABC News the budget is “scant on details regarding Social Security.”

Asked during Friday’s press briefing why a solvency pitch wasn’t included in the budget, Office of Management and Budget Director Shalanda Young said, “We’re trying to protect the benefits that are there now.”

“I wish we were at the point of the debate where we could sit down and come up with proposal to extend [solvency]. Unfortunately, it’s clear some people want to go backwards … You’re assuming all players are starting from the same place, they’re not,” Young said.

The problem for Biden, experts said, is that he’s vowed not to cut any benefits and to not increase taxes on those making under $400,000 per year — which will make it extremely difficult to balance the program’s finances long-term.

“Under the parameters that President Biden has set out, it’s almost mathematically impossible,” Biggs said.

During the 2020 campaign, Biden proposed upping the payroll tax to 12.4% for Americans making more than $400,000 per year, among other changes, to help Social Security’s funding shortfall. An analysis by the public policy think tank Urban Institute found those changes would extend Social Security’s solvency just five years.

“To fix the problem, what he’d have to do is he’d have to find more money or he’d have to cut benefits,” Richard Johnson, the director of the Urban Institute’s Program on Retirement Policy, told ABC News.

“Changes to Social Security have always been bipartisan, and so it might not be something that he wants to do on his own because it will probably involve some pain,” Johnson said.

The 2024 budget stated the administration looks forward to “working with Congress to responsibly strengthen Social Security by ensuring that high-income individuals pay their fair share.”

Republicans have been critical of Biden’s new budget proposal, rejecting any tax increases.

GOP leaders have said Social Security and Medicare will not be touched during negotiations on the debt limit, though some in the party have previously called for cuts and others have advocated for changes to benefit formulas or the eligibility age.

Treasury Secretary Janet Yellen, testifying on the budget on Capitol Hill Friday, was asked by Democratic Rep. John Lawson about payroll tax increases for those earning over $400,000 per year to help fund Social Security.

“I think it is about fairness and I think hardworking Americans who have counted on Social Security and paid into it their entire lives and depended on it as their major source of income in retirement, I think we need to make sure that it’s there for them,” Yellen said. “And we look for additional revenue to Americans with very high incomes, many of whom in total pay less taxes than a teacher or a firefighter.”

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