Treasury Secretary Timothy Geithner told lawmakers that failure to raise the federal government’s debt limit would bring “severe hardship” for Americans as the government would be forced to suspend services such as Social Security payments, Bloomberg reported.

Geithner, in a letter to members of Congress, said the United States will reach the $14.29 trillion limit on its ability to borrow no later than May 16 if Congress doesn’t act. Republican lawmakers have been resisting a debt-limit increase while calling for extensive budget cuts.

“The longer Congress fails to act, the more we risk that investors here and around the world will lose confidence in our ability to meet our commitments and our obligations,” Geithner wrote in a letter addressed to Senate Majority Leader Harry Reid.

Geithner’s warning came as lawmakers debated budget legislation needed to avert a government shutdown on Friday, when existing spending authority expires. House and Senate negotiators, joined by the White House, are considering plans to reduce the budget by about $33 billion. Lawmakers have passed $10 billion in cuts so far for the fiscal year.

House of Representatives Budget Committee Chairman Paul Ryan is set to outline a budget plan on Tuesday that is expected to propose phasing out traditional pay-for-service Medicare and instead provide government subsidies for the elderly to obtain health care through private insurers, Reuters reported. Ryan said in an interview that Medicare “crowds out all other government spending.”