Rutte made the remarks on CBS News's "Face the Nation with Margaret Brennan" on March 22, after Israel said that Iran could strike European capitals.
Asked if NATO shared Israel's assessment that Iran's missiles could hit Berlin, Paris, and Rome, Rutte said the military alliance "cannot confirm that at the moment, so we're looking into that."
"What we know for sure is that they are very close to having that capability, whether this case with the UK base, Diego Garcia, we are still assessing," he said. "But if it is true, it means they already have that capability. If it is not true, we know they are very close to having that capability."
Speaking to the BBC's Laura Kuenssberg on March 22, a British government minister said that two ballistic missiles had been fired at Diego Garcia, but neither hit the island.
"Our assessment is that the Iranians certainly targeted Diego Garcia. As we understand it, one missile fell short—failed—the other was intercepted," Housing Secretary Steve Reed said.
Reed said he would not share how far the missiles fell short for security reasons, but added that the British military has the capabilities on the ground to intercept and prevent such strikes.
He further said that there is no assessment that Tehran was targeting the UK, "or even could, if they wanted to."
British Prime Minister Sir Keir Starmer echoed those remarks, telling reporters on March 23 that there had been no assessment that the UK mainland was being targeted by Tehran.
Rutte Praises Trump
Rutte, who has consistently supported U.S. President Donald Trump, praised his efforts to take out Tehran's military capabilities.
"If Iran would have the nuclear capability, including, together with the missile capability, it will be a direct threat, a existential threat, to Israel, to the region, to Europe, to the stability in the world," Rutte told CBS News.
"So the president doing this is crucial, and I've seen the polling, but I really hope the American people will be with him, because he is doing this to make the whole world safer."
He also credited Trump with getting NATO allies—the vast majority of which are in Europe—to agree to increase their own defense spending.
"What I know is that we always come together. It was under President Trump's leadership that we had the extremely successful Summit in the Hague where we agreed to spend 5 percent of our [gross domestic products] on defense, and therefore equalizing for the first time since [President Dwight D.] Eisenhower," he said.
Responding to Rutte's remarks in a March 23 post on X, Iranian Foreign Ministry spokesperson Esmail Baghaei said, "That even the NATO Secretary General (who is infamously pressing Alliance members to appease the U.S. and support their illegal war on #Iran) declines to endorse Israel's most recent disinformation, speaks volumes: the world has grown thoroughly exhausted with these tired and discredited 'false flag' storylines."
A false flag operation is an act carried out with the intent to make it appear as though the other party was responsible.