While President Donald Trump and Secretary of State Mike Pompeo have been unequivocal in their assertion that Iran was responsible for the attacks on two oil tankers in the Gulf of Oman last week, some of America’s closest allies are demanding more proof.

Both Japan and Germany have requested more concrete evidence to support the Trump administration’s insistence that Iran was behind the twin attacks on the Norwegian-owned Front Altar and the Japanese-owned Kokuka Courageous near the Strait of Hormuz on Thursday.

Following the explosions, the U.S. released a grainy video that allegedly showed an Iranian patrol boat removing an unexploded mine from the Courageous shortly after the initial blast.

The footage, Trump said Friday, was proof that “Iran did do it.”

“You know they did it because you saw the boat,” he told “Fox & Friends.”

But U.S. allies ― and the owner of the vessel itself ― have disagreed with this conclusion. The president of Kokuka said at a press conference that the Courageous appeared to be struck by something that “flew towards the ship,” and not by a mine as the Trump administration has suggested.

“I do not think there was a time bomb or an object attached to the side of the ship,” Yutaka Katada said.

A senior Japanese government official told Japan Today that “the U.S. explanation has not helped us go beyond speculation.”

German Foreign Minister Heiko Maas said Friday that “the video is not enough.”

“We can understand what is being shown, sure, but to make a final assessment, this is not enough for me,” Maas told reporters.

Jeremy Corbyn, Britain’s opposition leader, said more “credible evidence” was needed to support Trump’s allegation. However, UK Foreign Minister Jeremy Hunt said Britain is “almost certain” Iran was behind the attacks.

According to The New York Times, other European leaders have also been hesitant to lay the blame on Iran ― a doubt fueled in part by their “distrust of the Trump administration and its hawkish policy toward Tehran,” the paper said.