Washington DC - President Donald Trump may face a revolt from key Senate Republicans, who threatened to block his budget bill over concerns about the national debt.

Trump was warned by Republicans that they must "get serious" about cutting spending and reducing the national debt or face a blockage in the Senate.

"I think we have enough to stop the process until the president gets serious about spending reduction and reducing the deficit," Wisconsin Senator Ron Johnson told CNN's Jake Tapper on Sunday.

Only three Republicans need to dissent to effectively block the "Big Beautiful Bill" from passing. The legislation only made it through the House of Representatives by one vote last week.

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The bill, which essentially pays for extending Trump's tax cuts – mostly favoring the wealthiest Americans – by slashing Medicaid access and food stamps for millions of Americans, is expected to add up to $4 trillion of debt.

"We need to be responsible," Johnson told Tapper. "The first goal of our budget reconciliation process should be to reduce the deficit."

Johnson, whose faction believes the cuts social welfare cuts don't go far enough, proposed immediately reducing the budget to pre-pandemic levels to create a benchmark for future cuts, but did not indicate where those additional cuts would be made.

"We need to focus on spending, spending, spending," said Johnson. "You don't defeat the deep state by funding it."