SOFIA, Bulgaria — A top European Union official branded President Donald Trump selfish and capricious Wednesday as E.U. leaders met to count the likely economic damage U.S. policies might inflict on the bloc and to try to rescue the Iran nuclear deal.

In a striking rhetorical assault on the leader of Europe's biggest ally, E.U. Council President Donald Tusk said, given Trump's recent decisions, "someone could even think 'with friends like that, who needs enemies?'"

Trump has bewildered the Europeans by threatening to slap tariffs on EU steel and aluminum exports and reneging on an agreement to stop Iran from developing nuclear weapons, which the E.U. believes is vital to world security.

Trump has also broken with a key international principle of Middle East peace efforts by moving the U.S. embassy in Israel to Jerusalem from Tel Aviv.

Some EU leaders have made a direct link between the move and the killing of dozens of Palestinians during protests on the Gaza border.

Tusk's remarks, made before he chaired a meeting in Bulgaria of the 28 leaders whose countries make up the world's biggest trading bloc, underscored the widening gulf in E.U.-U.S. relations.

Listing Europe's traditional challenges, ranging from the expanding power of China to the belligerence of Russia, Tusk said: "We are witnessing today a new phenomenon, the capricious assertiveness of the American administration."

"Frankly speaking, Europe should be grateful to President Trump because thanks to him we have got rid of all illusions. He has made us realize that if you need a helping hand, you will find one at the end of your arm," Tusk said.

"Europe must do everything in its power to protect, in spite of today's mood, the transatlantic bond. But at the same time we must be prepared for those scenarios, where we will have to act on our own," continued Tusk, a former Polish prime minister.

At dinner talks in the Bulgarian capital of Sofia, E.U. leaders were briefed on possible incentives to keep Tehran in the nuclear agreement despite a key player like the U.S. pulling out. Trump's decision means that U.S. sanctions, held in check by a presidential veto until now, could soon hit Iran and European companies doing business there.

The options being considered include new credit lines for Iran, increased energy cooperation and the use of E.U. laws to block European companies from caving in to U.S. sanctions.

The leaders also planned to discuss Trump's steel and aluminum tariffs, which could be imposed on the E.U. after June 1. Trump says the tariffs are needed for national security reasons.

Europe's leaders, most of whom govern nations that are NATO allies with the U.S., say security concerns simply are an excuse to break with the rules-based order of the World Trade Organization.

"It is absurd to even think that the E.U. could be a threat to the U.S. We need to bring back reality in this discussion," Tusk said.

A former U.S. envoy to the E.U., Anthony Gardner, told the European Parliament on Wednesday that "the broader U.S.-EU security relationship is at risk."

Trump is due to meet with NATO Secretary General Jens Stoltenberg at the White House on Thursday to discuss a range of issues.

A NATO spokesperson told NBC News that no changes have been made to Stoltenberg's schedule after the president’s public schedule was released Wednesday night with no mention of a planned joint news conference with the two leaders. The meeting remains scheduled on the NATO website.

"You’d have to ask the White House about any changes to the schedule," the spokesperson said. "We’ll have to see tomorrow."