The North Atlantic Treaty Organization provides "actual security" for America, the State Department said Monday, amid a controversy over former President Donald Trump's recent suggestion that he would "encourage" Russia to attack NATO members if they fail to fulfill their spending obligations.

Matthew Miller, the department's spokesperson, made the point as Trump's remarks raised concerns that the United States' security commitments to NATO and other alliances could erode should Trump return to the White House.

"I would just say, as we often say, that the NATO Alliance provides actual security to the American people," Miller told a press briefing. "This isn't just a benefit. ... This isn't just an alliance that the US puts into. We also get a lot out of this alliance."

Miller also pointed out that the transatlantic alliance came to the defense of the US after the Sept. 11 terrorist attacks in 2001.

"The only time that NATO has ever come to the defense of one of its member countries, it was coming to the defense of the United States after 9/11," he said. "We have been heartened by the broad support for NATO from the American people. We have been supported ... been heartened by the broad support for NATO from Congress."

Last week, Trump said that he would "encourage" Russia to "do whatever the hell they want" to "delinquent" NATO countries that fail to meet their spending obligations to the alliance.

The remarks deepened speculation among observers that a second-term Trump administration could turn to an isolationist approach that would see the US curtail its global security role and heap pressure on allies to do more for their own security.

The remarks drew immediate pushback, including from President Joe Biden. In a statement, Biden lambasted the remarks as "appalling and dangerous." (Yonhap)