U.S. President Donald Trump said he believed Britain would fight to defend the United States but suggested he could not say the same for the European Union, a factor in his decision not to sign a trade deal with the bloc.

Trump told the BBC in an interview published on Tuesday that he also still had doubts about support from NATO members, even after they agreed to increase defence spending.

“One of the problems with NATO, as I said, we have to fight for them, but will they actually fight for us if we had a war?”

“And I’m not sure I can say it, but I will say this, I believe that the UK would fight with us,” he said.

“I think that they would be with us. I’m not sure that a lot of the other countries would be.”

Trump said this was a factor in his willingness to grant Britain some exemptions from his tariff programme. In contrast, he has threatened a 30% tariff on European goods.

“Look, that’s why I made a deal with them, and I haven’t made a deal, I mean, I’ve made some other deals, but for the most part, in terms of your competitors, and in terms of the European Union, I haven’t made a deal,” he told the BBC.

The only time NATO has activated Article 5 – the cornerstone of its founding treaty which stipulates that an attack on one is an attack on all – was on behalf of the United States, in response to the Sept. 11, 2001 attacks.

British troops supported the U.S. in conflicts that followed in Afghanistan and Iraq but since then, the army has reduced in size.