Senate Majority Leader John Thune, R-S.D., said Thursday that any move by President Donald Trump to withdraw the United States from NATO would require congressional approval.
The announcement contradicted Trump's recent assertion that he could act unilaterally.
In an exclusive interview with the Washington Examiner, Thune said Congress would play a decisive role in any such decision.
"I don't think you can make that kind of a decision unilaterally," he said, adding that lawmakers would "want to be heard from" on an issue of that magnitude.
Thune's comments follow Trump's remarks earlier this week in which he said he was "disappointed" in NATO and suggested the U.S. leaving the alliance is "certainly something we should think about."
Trump has argued he has the authority to withdraw without Congress, though a 2023 law requires either a two-thirds Senate vote or separate legislation to exit the alliance.
Despite defending NATO as "probably the most effective alliance in history," Thune echoed a key Trump criticism: that the United States has long borne a disproportionate share of the defense burden.
He credited Trump with pressuring NATO members to increase military spending, a long-standing demand that allies meet a target of at least 2% of GDP on defense.
Trump has repeatedly used that benchmark to criticize European allies, warning during his presidency and afterward that the U.S. might reconsider its commitments if countries fail to meet spending goals.
His administration's pressure campaign led to increased defense outlays among several NATO members, though compliance has remained uneven.
Tensions have escalated further in recent days over security in the Strait of Hormuz, a critical transit route carrying roughly 20% of the world's oil supply.
After Iran shut down the passage following U.S. military strikes, Trump publicly vented frustration that NATO allies were not contributing more to maritime security operations.
The president also pointed to U.S. spending on Ukraine's war effort as evidence of what he described as an imbalanced relationship with allies, calling it a "one-way street," even though Ukraine is not a NATO member and European countries have also provided substantial aid.
The prospect of withdrawing from NATO has exposed divisions within the Republican Party. Rep. Don Bacon, R-Neb., warned earlier this week that such a move would spark a "civil war" within GOP ranks, saying many Republicans view the alliance as essential to countering threats from Russia and China.
Thune's remarks underscore that divide: while many Republicans support Trump's push for greater burden-sharing, there remains strong institutional resistance in Congress to abandoning the decades-old alliance altogether.
James Morley III ✉
James Morley III is a writer with more than two decades of experience in entertainment, travel, technology, and science and nature.
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