Iran has sent two warships to the Gulf of Aden, according to state media reports, establishing a military presence off the coast of Yemen where Saudi Arabia is leading a bombing campaign to oust the Iran-allied Houthi movement.
The Alborz destroyer and Bushehr support vessel sailed from Bandar Abbas on a mission to protect Iranian shipping from piracy, Rear Admiral Habibollah Sayyari said in comments quoted by Press TV.
Saudi Arabia and several Arab allies have been carrying out an air and naval blockade on Yemen as part of a two-week campaign to oust the Houthis, who have taken most of the country.
Iran has condemned the Saudi-led campaign and called for dialogue.
Saudi Arabia accuses Iran of providing military support to the Houthis, a charge the Islamic Republic denies.
Mr Sayyari said the Iranian ships will patrol the Gulf of Aden, south of Yemen, and the Red Sea.
The area is one of the world's most important shipping routes and a gateway between Europe and the Middle East.
Meanwhile, the United States has stepped up weapons deliveries in support of the Saudi-led coalition resisting the advance of Shia rebels in Yemen, a senior US official said yesterday.
"Saudi Arabia is sending a strong message to the Houthis and their allies that they cannot overrun Yemen by force," Deputy Secretary of State Antony Blinken told reporters in the Saudi capital.
"In support of that effort we have expedited weapons deliveries," he said after talks with Defence Minister Mohammed bin Salman and other Saudi officials.
The coalition on 26 March began air strikes in Yemen, aiming to defeat the Houthi rebels who seized power in the capital Sanaa in February.
It was feared that the rebels would take over the entire country and shift it into the orbit of Shia Iran, Sunni Saudi Arabia's regional rival.
The Houthis, allied with army units loyal to ex-president Ali Abdullah Saleh, have been fighting forces loyal to Mr Hadi, who fled to the Saudi capital Riyadh late last month from the port city of Aden.
Mr Blinken said Mr Hadi's opponents "have brought Yemen to the brink of economic collapse" and demolished government institutions in a country which had been "on a very positive path to an inclusive future".
Al-Qaeda and other groups were seeking to exploit the resulting instability, he said.
"These security threats extend beyond Yemen to the region and indeed to the entire world."
Mr Blinken, who is on a Middle East tour, met with Mr Hadi during his Riyadh stop.
The US official said it "is more important than ever" that the US and the Gulf Cooperation Council states, which include Saudi Arabia, coordinate closely and press all parties especially the Houthis and their allies "to commit to a consensus political solution".
Mr Blinken also offered reassurances that a framework agreement reached last week to curb Iran's nuclear drive would make the Gulf safer.
"Iran without a nuclear weapon will be less emboldened to take destabilising activities in the region.
"We will reduce the pressure for a regional arms race... this agreement is a critical step in ensuring greater security in the Gulf," he said.
The deal marked a major breakthrough in a 12-year standoff between Iran and the West, which has long feared Iran wants to build an atomic bomb, despite Iran's denials.
Saudi Arabia worries that if too much of Iran's nuclear programme is left intact it will still have the ability to obtain an atomic bomb, and there have been concerns that Saudi Arabia could seek its own nuclear capability.