"He is clearly disappointed with many NATO allies, and I can see his point," Rutte told CNN after spending more than two hours at the White House on Wednesday.
"This was a very frank, very open discussion, but also a discussion between two good friends."
Rutte spoke hours after White House spokeswoman Karoline Leavitt quoted Trump as saying of NATO: "They were tested, and they failed," during the Iran war.
Several NATO countries resisted supporting the US military campaign against Iran by denying US military planes use of their airspace or declining to send naval forces to help reopen the Strait of Hormuz for energy tankers.
Without specifying the countries, Rutte said his own view was that "some" NATO countries had failed to live up to their commitments in the Iran operation but that "the large majority of Europeans" had been helpful.
The White House did not disclose details of the talks.
Trump has repeatedly called NATO a "paper tiger" and threatened to withdraw from the 32-member transatlantic alliance in recent weeks, arguing that Washington's European allies have relied on US security guarantees while providing inadequate support for the US-Israeli bombing campaign in Iran.
Although Trump on Tuesday said the attacks on Iran would be paused under a two-week ceasefire, the fallout from the conflict has continued to strain ties between Washington and its allies, suggesting the diplomatic consequences may linger longer.
Leavitt on Wednesday said NATO countries had "turned their backs on the American people," who fund their nations' defence, and that Trump would have a "very frank and candid conversation" with the NATO chief.
Trump has called for countries that depend on oil from the Gulf region to break Iran's chokehold on the Strait of Hormuz, but European countries are unlikely to join mine-clearing or other missions to free up navigation as long as hostilities continue, according to two European diplomats.
Rutte, known in Europe as a "Trump whisperer," has cultivated a warm relationship with Trump despite the tensions and referred to the president in 2025 as a "daddy" handling a schoolyard brawl between Israel and Iran.
Another European diplomat described Rutte's approach to Trump as deferential but effective.
A NATO official said Rutte, while at the White House, would seek to increase defence-industry co-operation and to discuss the wars in Iran and Ukraine.
NATO is a defensive alliance focused on North America and Europe, and it was not clear precisely what role Trump expected it to play in the Middle East.
NATO, which includes European countries, the United and Canada, was formed in 1949 to counter the risk of Soviet attack and has been the cornerstone of the West's security ever since.
