Graham, a staunch supporter of Ukraine, made the comments in an interview at the Munich Security Conference, where top U.S. and European officials have gathered to discuss the war in Ukraine, among other issues.

“If you can’t get them into NATO right now, my idea with Boris Johnson is to be really clear: Tell Putin if you ever do this again, if there’s another incursion by Russia into Ukraine, that leads to automatic admission into NATO by Ukraine as a tripwire,” the South Carolina senator said.

Graham also sought to cast aside the attention given to Hegseth’s comments from earlier this week when he said that the United States does not believe “NATO membership for Ukraine is a realistic outcome of a negotiated settlement,” stressing that all that matters is how the three-year war ends.

“It doesn’t matter what Pete says, it doesn’t matter how many phone calls are made. What matters is how it ends, if it ends in a way to deter future aggression and if they’ve stabilized the continent of Europe, [Trump will] get his fair share of the credit,” he said.

Graham concluded by urging the U.S. to continue supplying Ukraine with U.S. weapons, including F-16s which former President Joe Biden greenlighted to the country after initial opposition, in order to “build up the capability of the Ukrainian military.” Trump, while eager to reach a deal to end the war, previously floated the idea of continued U.S. aid in exchange for rare minerals in Ukraine. Ukrainian President Volodymyr Zelensky voiced his strong approval of the idea, and U.S. Treasury Secretary Scott Bessent was sent to Ukraine earlier this week to continue those discussions.

On separate negotiations to end the war, Trump held a call with Russian President Vladimir Putin this week and both agreed to start those peace talks “immediately.” Those talks may not include European nations after Trump’s special envoy for the conflict suggested that they find other ways to be helpful in the negotiations, including by increasing defense spending.

Graham warned on Saturday that if Putin rejects a Trump-minted deal, he “will be making a serious mistake.”