"I know that a lot of Republicans, their dream is to cut Social Security and Medicare," Biden said during a trip to the Republican stronghold of Florida, which has one of the highest number of people without health insurance.

"Well, let me say this: if that's your dream, I'm your nightmare."

Even though he has not yet officially declared his candidacy, Biden appeared to be speaking with an eye to the 2024 presidential election.

The speech borrowed from Biden's State of the Union address Tuesday, when he blasted Republicans for seeking to cut social spending in order to lower the country's huge debt.

That caused aggressive jeering from many Republican members of Congress, one of whom shouted "Liar!" at the president.

Some Republicans in the audience also shouted that they did not intend to take away the benefits, but Biden was skeptical about those promises on Thursday, saying "I'll believe it when I see it."

Some 18 percent of Americans are on Medicare, federal health insurance for people 65 or older, and other people with certain disabilities.

Medicaid is a separate program partly financed and operated by states that covers medical costs for low-income Americans of all ages.

Speaking in a state that has a large population of seniors and also 5.5 million low-income people on Medicaid, Biden blasted Florida Governor Ron DeSantis for blocking the expansion of Medicaid.

"Over 1.1 million (more) people in Florida would be eligible for Medicaid if Governor DeSantis just said, 'I agree to expand,'" Biden said. "The only reason Medicaid expansion hasn't happened here is politics."

Biden, who says he hasn't yet made a final decision on whether to run for a second term next year, is betting heavily on boosting social programs to rally voters.