"I think we have a lot of foes," Efe quoted Trump as saying to CBS Evening News in response when anchor Jeff Glor asked him to name his "biggest foe globally right now".

"I think the European Union is a foe, what they do to us in trade. Now, you wouldn't think of the European Union, but they're a foe," the President said.

"Russia's a foe in certain respects," Trump said, adding, "China is a foe economically, certainly they are a foe. But that doesn't mean they are bad. It doesn't mean anything. It means that they are competitive. They want to do well and we want to do well."

The Trump administration has imposed tariffs on imports from EU countries, China, and even Canada and Mexico, prompting retaliatory measures by those nations.

Before and during the NATO summit, the US President again berated European nations for falling short of the alliance's goal to have all member-states devote 2 per cent of GDP to the military.

"I respect the leaders of those (European) countries," Trump said. "But, in a trade sense, they've really taken advantage of us and many of those countries are in NATO and they weren't paying their bills."