Several U.S. Navy ships crossed the Strait of Hormuz on Saturday, a U.S. official told Axios. Why it matters: The move was not coordinated with Iran. It is the first time U.S. warships crossed the strait since the beginning of the war.The operation was aimed at increasing confidence for commercial ships to cross, sources say. It came as peace talks between the two sides kicked off in Pakistan. "This was an operation that focused on freedom of navigation through International waters," the U.S. official said.Driving the news: The official said the Navy ships crossed the strait from east to west to the Gulf, and then made their way back through the strait to the Arabian Sea. The Iranian government reportedly called the crossing a ceasefire violation and threatened to attack the ships, per state media reports.The big picture: The reopening of the strait was a key provision in the U.S.-Iran ceasefire deal. The narrow waterway off Iran's southern coast is vital to the normal functioning of the global economy.For several days after the ceasefire was announced very few ships crossed. There were reports Saturday morning that at least three oil-carrying supertankers crossed — a tentative sign of movement, though a tiny fraction of normal. A U.S. official admitted earlier this week that ships were not moving through because they were intimidated by the Iranians. What they're saying: President Trump posted on Truth Social on Saturday that the threat that a ship may "bunk" into sea mines was the only thing Iran had to intimidate them from crossing the strait. 'We're now starting the process of clearing out the Strait of Hormuz as a favor to Countries all over the World, including China, Japan, South Korea, France, Germany, and many others," he wrote. Editor's note: This story has been updated with additional details on the crossing.