An Iranian cargo ship heading to Yemen is expected to cross into the Red Sea on Thursday, state news agency IRNA reported, amid fears of a showdown with Saudi-led forces enforcing restrictions on Yemeni ports.
The approaching vessel threatens to broaden a regional confrontation over Yemen -- where Saudi Arabia and its Sunni Muslim allies have launched almost two months of attacks on Houthi fighters it says are armed by Shi'ite power Iran. Tehran dismisses the allegation.
"If the weather and the ship's technical conditions persist ... we will enter the Bab al-Mandeb strait tomorrow morning," the Iran Shahed's captain Massoud Ghazi Mirsaid was quoted as saying on Wednesday, referring to a stretch of water linking the Gulf of Aden with the Red Sea.
Reuters ship tracking data showed the Iran Shahed positioned south of Aden at 1015 GMT on Wednesday. Lebanon-based al-Mayadeen television said the ship would arrive on Thursday though and activist on board told journalists it would dock on Friday.
By crossing the strait, the Iran Shahed will sail past Djibouti where the United Nations is co-ordinating aid for Yemen. U.S. officials have called on Iran to divert the ship to Djibouti to allow the ship's cargo to be inspected.
Iran has said the ship is carrying 2,500 tonnes of food and medical supplies to Yemen's Hodaida port to help people caught up in the conflict.
Residents said on Wednesday warplanes from the Saudi-led coalition had carried out the most sustained bombardment of Yemen's capital Sanaa in nearly two months of air strikes overnight, hitting army bases and weapons depots.
The coalition has been bombing Houthi forces since March 26 in a bid to restore Yemeni President Abd-Rabbu Mansour Hadi to power after fighters from the Shi'ite Muslim group forced him to flee the country.
Saudi-led forces have imposed searches on all ships trying to enter Yemen in a bid to prevent weapons being smuggled to the Houthis who control much of the country, including Hodaida.
Sunni Muslim Saudi Arabia and regional Shi'ite powerhouse Iran are in a tussle over influence in the Middle East, where sectarian tensions are fuelling civil wars that have killed hundreds of thousands of people.
Iran has condemned the Saudi-led air strikes in Yemen and officials in Tehran have said they will not let Saudi-led forces inspect the cargo ship.
Deputy Chief of Iran's Armed Forces Brigadier General Massoud Jazayeri said last week that any attack on the ship would spark a regional war.
The Pentagon said on Tuesday the Iran Shahed had linked up with two Iranian warships as it passed through the Gulf of Aden, though that report was disputed by two foreign activists on board.
Pentagon spokesman Colonel Steve Warren said on Tuesday that the ships' locations were being monitored "every step of the way."