Vice President Biden reassured NATO allies Tuesday that the United States will defend them from an attack, despite misgivings about the North Atlantic treaty from Republican presidential candidate Donald Trump.

Referring to Trump as "a presidential candidate in the other party," Biden told Baltic state leaders that Trump's hesitation to defend NATO allies is "nothing that should be taken seriously, because I don't think he understands what Article 5 is."

Article 5 is the provision in the NATO treaty that requires all allies to respond collectively to an attack on any one ally. It's been invoked only once, by the United States, in response to the terrorist attacks of 2001.





"I want to make it clear, absolutely clear to all the people of the Baltic States, we have pledged our sacred honor — the United States of America — our sacred honor to the NATO treaty," Biden said in Riga, Latvia, where he also met with the leaders of Estonia and Lithuania. "We mean what we say, we have never reneged on any commitment we have made. Our sacred honor is at stake."

Trump has rattled NATO allies with a number of pronouncements about the 67-year-old treaty organization, complaining that European allies aren't paying their fair share on defense and suggesting that NATO needs to transition from a Cold War-era check on Russian power to am alliance that can cope with the modern-day threats of terrorism.

President Obama has voiced those same concerns over the years. But in what would be a reversal of U.S. policy, Trump has suggested that he would make the mutual defense of NATO allies contingent on whether an attacked country pays the benchmark 2% of its economy on military spending. (Estonia is one of five NATO allies to meet that threshold.)

In an interview with the New York Times last month, Trump said he'd like NATO allies to pay their dues. But if they don't, "I would be absolutely prepared to tell those countries, 'Congratulations, you will be defending yourself.'"

It appeared that the Baltic State presidents were reassured by Biden's visit. Speaking at a joint press conference, Estonian President Toomas Hendrik Ilves said "for us we have never doubted" Article 5.

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Lithuanian President Dalia Grybauskaite said the NATO alliance is "already long-lasting" and that she was sure it would continue after the elections "no matter what."

Biden began a a four-day foreign trip Monday that will also include stops in Ankara, Turkey and Stockholm, Sweden.

It's unusual for a president or vice president to bring up campaign politics while overseas. But White House Press Secretary Josh Earnest said the remarks were appropriate given the concern by NATO allies.

"I did not see the entirety of the vice president's remarks but I am confident that his remarks were an effort to clear up any confusion that may exist on this front — and some of that confusion may stem from some of the rhetoric that we've seen on the campaign trail," Earnest said Tuesday.