DUBAI, United Arab Emirates (AP) — The United States will launch an effort today to “guide” stranded ships from the Iran-gripped Strait of Hormuz, President Donald Trump said, giving few details about a sweeping effort to help hundreds of vessels and some 20,000 seafarers.

Trump said in a social media post on Sunday that “neutral and innocent” countries have been affected by the Iran war, and “we have told these Countries that we will guide their Ships safely out of these restricted Waterways, so that they can freely and ably get on with their business.”

“Project Freedom” would begin this morning in the Middle East, Trump said, adding that his representatives are having discussions with Iran that could lead to something “very positive for all.”

Iran’s effective closure of the strait, imposed after the U.S. and Israel launched the war on Feb. 28, has shaken global markets.

Ships and seafarers, many on oil and gas tankers and cargo ships, have been stuck in the Persian Gulf since the war began. Crew members have described to The Associated Press watching intercepted drones and missiles explode over the waters, and running low on drinking water, food and other supplies.

Many sailors come from India and other countries in south and southeast Asia.

“They are victims of circumstance,” Trump wrote, and described the effort as a humanitarian gesture “on behalf of the United States, Middle Eastern Countries but, in particular, the Country of Iran.” But he sounded a warning: “If, in any way, this Humanitarian process is interfered with, that interference will, unfortunately, have to be dealt with forcefully.”

Trump’s statement was quickly shared by some Iranian outlets, which described his announcement as a “claim.”

Trump spoke hours after Iran said it was reviewing the U.S. response to its latest proposal to end the war and made clear these are not nuclear negotiations. The fragile three-week ceasefire appears to be holding.

Earlier Sunday, a cargo ship near the Strait of Hormuz said it was attacked by multiple small craft, the British military’s United Kingdom Maritime Trade Operations center reported. It was the latest in at least two dozen attacks in and around the strait since the Iran war began.

All crew on the unidentified northbound cargo ship were safe after the attack off Sirik, Iran, east of the strait, the British monitor said. Iranian officials have asserted that they control the strait and that ships not affiliated with the United States or Israel can pass if they pay a toll, challenging the freedom of navigation guaranteed by international law.

Iran denied an attack, the semiofficial Iranian outlets Fars and Tabnak reported, and said a passing ship had been stopped for a documents check as part of monitoring.

The monitor said it was the first reported attack in the area since April 22. Tehran has effectively closed the strait by attacking and threatening ships, and the threat level in the area remains critical.

Iranian patrol boats, some powered only by twin outboard motors, are small, nimble and hard to detect. Trump last month ordered the U.S. military to “shoot and kill” small Iranian boats that deploy mines in the strait.

The British military monitor also said Sunday it had received reports that ships near Ras al-Khaimah, the northernmost emirate in the United Arab Emirates and close to the strait, have received radio warnings to move from anchorages. It was not clear who sent the VHF messages.

Tehran is reviewing the U.S. response to its latest proposal to end the war, Iran’s judiciary Mizan news agency cited Foreign Ministry spokesman Esmail Baghaei as saying.

But “at this stage, we have no nuclear negotiations,” Baghaei said. Iran’s nuclear program and enriched uranium have long been the central issue in tensions with the U.S., but Tehran would rather address it later.

Iran’s proposal wants other issues resolved within 30 days and aims to end the war rather than extend the ceasefire, according to Iran’s state-linked media.

Trump on Saturday said he was reviewing the proposal but expressed doubt it would lead to a deal.