Then-Secretary of State John F. Kerry speaks about Israeli-Palestinian policy in December 2016. (Andrew Harnik/AP)

Former U.S. secretary of state John F. Kerry on Wednesday accused President Trump of “strange” and “counterproductive” behavior at the outset of a NATO gathering and said Trump is “steadily destroying our reputation in the world.”

The unusually harsh assessment from the country’s former top diplomat came after Trump said at a breakfast meeting in Brussels that he considers Germany to be “captive to Russia” because it is getting much of its energy from the nation, and continued his attacks on other allies for their levels of defense spending.

“I’ve never seen a President say anything as strange or counterproductive as President Trump’s harangue against NATO and Germany,” Kerry said in a statement distributed over Twitter. “It was disgraceful, destructive and flies in the face of the actual interests of the United States of America.”

Trump’s participation in the meeting of leaders of the North Atlantic Treaty Organization comes days before he is set to hold a summit with Russian President Vladi­mir Putin in Helsinki — a meeting Kerry also referenced in his statement.

“President Trump makes public adversaries out of our friends, and turns our adversary, who has been attacking America’s democracy, into his fawned-over ally. Why?”

“What was on display in Brussels today was not the behavior of a strong, principled, and wise leader,” Kerry said. “Enough. This isn’t good for the United States and there are people across the aisle — as the Senate vote yesterday clearly showed — who know it and need to say it.”

Kerry, a former Democratic senator from Massachusetts, was referring to a 97-2 vote in the Senate on Tuesday in a nonbinding motion supporting NATO.

After Trump’s broadside against Germany and other allies Wednesday, he joined other NATO leaders in backing a sweeping set of plans to bolster defenses against Russia and terrorism.

Wednesday was not the first time Kerry and Trump have tangled.

In May, Trump took to Twitter to castigate Kerry following a report that he was engaged in unusual shadow diplomacy in a bid to preserve the pact he helped negotiate to limit Iran’s nuclear program. Trump characterized Kerry’s actions as “possibly illegal” and said the deal had been “very badly negotiated.”

In a measured statement in response, a Kerry spokesman said Kerry “stays in touch with his former counterparts around the world just like every previous Secretary of State.”