The best way to deter conflict "is to be ironclad in our support for our NATO allies," Arkansas Sen. Tom Cotton said at the Defense One summit in Washington.
Cotton, a former Army infantry officer and veteran of Iraq and Afghanistan, was submitted as a potential pick by Vice Presidential-elect Mike Pence who is now leading transition efforts, a source told CNN Tuesday.
"NATO is not a charity," he said. "We are in NATO because it's a security alliance that protects our interests."
Trump has not publicly commented on NATO since winning the election, but during the campaign, the President-elect questioned whether the US would come to the defense of an alliance member if that country was not meeting its commitment to defense spending.
Only five of the 28 NATO members currently meet the recommended defense spending levels, which is 2% of GDP, though additional countries plan to meet that target in the coming years.
Cotton, though, drew a distinction between these financial commitments and the need to come to the defense of any NATO member that comes under attack.
"Article V is a treaty commitment. The 2% defense spend is a political commitment. There is a difference," Cotton said, referring to the mutual defense clause in the NATO founding treaty.
His strong endorsement of the defense alliance followed comments made by President Barack Obama Tuesday, where the President said that Trump had expressed support for NATO.
"I am encouraged by the President-elect's insistence that NATO is a commitment that does not change," Obama said Thursday while appearing alongside German Chancellor Angela Merkel in Berlin.
Cotton echoed this point in his comments.
"Donald Trump has spoken about, about upholding our obligations and our alliances as part of our core interests," he said.
Cotton also sounded a tough line on Russian and its leader Vladimir Putin.
"To improve our relations with Russia, what needs to happen foremost is that Vladimir Putin has to have a new sense of boundaries," he said.
Asked about whether he might be a candidate to head the Pentagon, Cotton demurred.
"President-elect Trump will make these decisions in his own due time," he said.