(CNN) If Congress doesn't act soon, tens of millions of Americans will only receive about three-quarters of their Social Security benefits when they retire.

Social Security's trust funds will be tapped out by 2035, according to an annual report released Monday by trustees of the government's two largest entitlement programs, the other being Medicare. That's one year later than last year's report projected.

The new projection doesn't mean retirees will no longer get checks in 16 years. But the program will at that point only have enough revenue coming in to pay three-quarters of promised benefits through the end of 2093.

The trustees urged lawmakers to act quickly to assure Americans they'll be able to get their full retirement benefits.

"Lawmakers have a broad continuum of policy options that would close or reduce the long-term financing shortfall of both programs," wrote Treasury Secretary Steven Mnuchin along with three other trustees, including Alex Azar, secretary of Health and Human Services, in their report to Congress.

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