An Iranian vessel pointed a weapon at a U.S. military helicopter in the Strait of Hormuz this weekend in the latest in a series of actions meant to harass U.S. assets in the area this year.

Reuters quoted two U.S. defense officials as saying the incident, which they described as “unsafe and unprofessional,” occurred Saturday. It was the first such incident since Donald Trump’s election Nov. 8.

There was no comment from the president-elect or his transition team.

The officials said the incident involved a Navy MH-60 helicopter that flew within a half-mile of two Iranian vessels in international waters, one of which aimed a weapon at the chopper.

"The behavior by our standards is provocative and could be seen as an escalation," the officials said.

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

Trump has been dismissive of Iran, ridiculing the harassment.

Tense relations with Iran eased somewhat after Tehran and world powers reached agreement on the country’s nuclear program. Serious differences remain, however, over Iran’s ballistic missile program and its involvement in the conflicts in Iraq and Syria.

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

Iranian Foreign Ministry spokesman Bahram Qassemi said last week there have been no talks with the United States on changing provisions of the agreement, denying a report in the Wall Street Journal 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.

Marine Gen. James Mattis, Trump’s reported favorite to be defense secretary, has 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.

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