Despite his rhetoric on defense spending, the president signed onto an agreement at the NATO summit that reiterated the mutual defense language included in Article 5 of NATO's founding document.
The agreement the president signed last week notes that any "attack against one Ally will be regarded as an attack against us all."
Article 5 is the bedrock principle of NATO and the reason it is widely considered the most powerful military alliance in the world. The last time NATO invoked Article 5 was after the Sept. 11 terrorist attacks on the United States.
Montenegro's prime minister was asked about Trump's interview Wednesday in parliament.
"He said that the Montenegrin people are brave and that he does not want the U.S. citizens to fight for others and for other NATO member states," Prime Minister Duško Marković said, according to an official translation provided to NBC News. "He did not say that only on that occasion, but he also said the same at the NATO summit, you know it because he said it publicly, not in terms of justification of NATO's existence, but of NATO funding."
According to NBC News, citing official figures, Montenegro contributes more troops per capita to the war in Afghanistan than the United States. Overall, Montenegro maintains a standing military of less than 2,000.
Montenegro joined NATO last year with the overwhelming consent of the U.S. Senate, which voted 97-2. Trump himself signed off on the country's entrance into the alliance.
The president's comments came just a day after his summit with Putin and raised concerns among some critics that the president is being too deferential to the Russian leader. Russia has historically opposed NATO's expansion — the alliance was formed to defend against the Soviet Union in the early days of the Cold War.
In 2015, a representative for Putin said that admitting Montenegro into the alliance would result in "retaliatory actions." After Montenegro acceded into NATO in 2017, the Russian foreign ministry issued a statement condemning the decision.