Republican nominee Donald Trump triggered alarm bells in Europe when he hinted Thursday he might not come to the defense of some NATO members if Russia were to attack.
Trump told The New York Times in a interview published on Thursday he would decide whether the Baltic republics had "fulfilled their obligations to us" in terms of their financial contributions to the alliance.
In a statement to NBC News, NATO's Secretary General Jens Stoltenberg said he will not interfere in the election, but called for unity.
"Solidarity among Allies is a key value for NATO," Secretary General Jens Stoltenberg said. "Two world wars have shown that peace in Europe is also important for the security of the United States."
NATO's treaty states that an attack on one member state constitutes an attack on all. Some analysts saw the remarks as carte blanche for Russia to intimidate NATO allies and a potential harbinger of the alliance's collapse were Trump to be elected.
Estonia's president was among the first to hit back, saying on Twitter that his nation has met its commitments and fought — "with no caveats."