European leaders alarmed by Trump’s NATO comments.

WASHINGTON — Alarm and condemnation erupted Thursday from European capitals, the White House and leaders of Donald Trump’s own party after the Republican presidential nominee suggested the United States might abandon its NATO military commitments if he were elected president.

Senate Republican leader Mitch McConnell, who backed Trump at the party’s national convention only two days earlier, said he totally disagreed with the statement but was willing to “chalk it up to a rookie mistake.”

McConnell called NATO “the most successful military alliance in the history of the world,” in a Facebook interview with The New York Times.

In Brussels, NATO Secretary-General Jens Stoltenberg said the alliance agreement was crystal clear: “We defend each other.”

“I will not interfere in the U.S. election campaign,” Stoltenberg said. But he pointedly added, “Two world wars have shown that peace in Europe is also important for the security of the United States.”

Secretary of State John Kerry reaffirmed the United States’ commitment to NATO. “This administration, like every single administration, Republican and Democrat alike since 1949, remains fully committed to the NATO alliance and to our security commitments under Article 5, which is absolutely bedrock to our membership and to our partnership with NATO.”

Indeed, Trump’s suggestion, in an interview with the Times, would upend decades of American foreign policy and rock the security structures that have underpinned European and global stability since the end of World War II.

Trump said in the Times interview that he would review allies’ financial contributions — in this case, those from Estonia, Latvia and Lithuania — before acting under NATO’s mutual defense clause, if any of the countries were attacked by Russia.

The U.S. accounts for more than 70 percent of all NATO defense spending, and only four other allies — Britain, Estonia, Greece and Poland — meet the minimum 2 percent of gross domestic product spending on defense that NATO requires.

Estonian President Toomas Hendrik Ilves tweeted that his country was one of the few to meet the minimum defense expenditure and noted pointedly that Estonia “fought, with no caveats” on behalf of the U.S. in Afghanistan.

A bitter foe within Trump’s own party, Sen. Lindsey Graham of South Carolina, said: “I’m 100 percent certain how Russian President (Vladimir) Putin feels — he’s a very happy man.”

Some Republicans opposed to Trump have indeed sought to cast him as pro-Putin, a position that would put him at odds with both Republican and Democratic foreign policy and also diverge from the current GOP party platform adopted at the convention.

Trump supporters succeeded in preventing a reference to arming Ukraine from getting into this year’s platform, but the manifesto itself is demonstrably not pro-Russia. It accuses “current officials in the Kremlin” of eroding the “personal liberty and fundamental rights” of the Russian people.”