Reuters quoted two U.S. defense officials who described the action as “unsafe and unprofessional.” It was the first incident since Donald Trump’s election November 8. Neither the president-elect nor his transition team commented.

Officials said that a Navy MH-60 helicopter flew within a half-mile of two Iranian vessels in international waters, and one of them aimed a weapon at the chopper. “The behavior by our standards is provocative and could be seen as an escalation,” the officials said.

Last September, a U.S. Navy coastal patrol ship was forced to change course when an Iranian fast-attack craft came within 100 yards.

President-elect Trump has been dismissive of Iran, and has ridiculed the harassment.

Relations with Iran eased after the nuclear agreement was reached between Tehran and world powers. Serious differences remain over Iran’s ballistic missile program and its involvement in the conflicts in Iraq and Syria.

Trump and Congress may undermine the deal, which the president-elect called a “disaster.” Rep. Mike Pompeo, R-Kansas, Trump’s pick to be head of the CIA, recently tweeted that he is eager to roll back the deal, which also involves Russia, China, France, Britain and Germany.

Bahram Qassemi, Iranian Foreign Ministry spokesman, said last week there have been no talks with the United States about changing the provisions of the agreement. He denied a report in the Wall Street Journal that officials held serious discussions about cutting the size of Iran’s nuclear stockpile to keep Trump from junking the agreement, the Tasnim news agency reported.

Trump’s reported favorite to be defense secretary, Marine Gen. James Mattis, said the U.S. should abide by the accord even though he thinks Iran is “the single most belligerent actor in the Middle East” and an “enduring threat to stability and peace” in the region, the Lobe Log on Foreign Policy reported.  “I want to make clear there’s no going back. Absent a clear and present violation [by Iran], I don’t think we can take advantage of some new president—Republican or Democrat—and say, ‘well, we’re not going to live up to our word in this agreement.’ I believe we’d be alone if we did, and unilateral economic sanctions from us would not have anywhere near the impact of an allied approach to this,” Mattis said.

The National Council of Resistance of Iran (NCRI) reported that last week Iran formally protested the votes in Congress extending sanctions against Tehran for 10 more years, and blocked aircraft sales to the regime.