Vice President Mike Pence: Russian ‘Aggression’ Makes NATO Necessary – NBCNews.com

Vice President Mike Pence speaks during a joint news conference with Estonia's President Kersti Kaljulaid, Lithuania's President Dalia Grybauskaite and Latvia's President Raimonds Vejonis in Tallinn, Estonia, on Monday. Ints Kalnins / Reuters

President Trump had previously

No other president since NATO was founded in 1949 had questioned that principle until Trump, although he recently expressed support for NATO's Article 5.

Pence also stated that recent diplomatic action by Russia will not impact American commitments to the security of its NATO allies.

Russian President Vladimir Putin said Sunday that he was

The move came in the wake of new sanctions voted through by the U.S. Congress last week which aim to punish Moscow for interfering in the 2016 presidential election and for its military aggression in Ukraine and Syria.

Recent diplomatic action taken by Moscow will not deter the commitment of the United States of America to our security, the security of our allies and the security of freedom loving nations around the world, Pence said.

[The U.S.] stands firmly behind our Article 5 pledge of mutual defense and an attack on one of us is an attack on us all, he added.

Estonian president, Kersti Kaljulaid, said the presence of Pence in Tallinn underlined the credibility of Article 5.

President Dalia Grybauskait of Lithuania, meanwhile, praised the decision of the U.S. Congress to pass new sanctions against Russia, describing it as a very good message.

Eoghan Macguire reported from London.

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Vice President Mike Pence: Russian 'Aggression' Makes NATO Necessary - NBCNews.com