May 26 (Reuters) - Iran said the United States had violated a ceasefire after the U.S. conducted what it called defensive strikes in southern Iran, while U.S. Secretary of State Marco Rubio said that negotiating a deal to halt the conflict could "take a few days".
Iran's foreign ministry said U.S. strikes in Iran's southern Hormozgan province, where Iranian media reported sounds of explosions early on Tuesday, represented a "gross violation" of a tenuous ceasefire in place for nearly seven weeks.
Both sides had indicated progress on a memorandum of understanding that could halt the war and restart shipping through the blockaded Strait of Hormuz, while giving negotiators 60 days to negotiate more complex issues including Iran's nuclear programme.
Following strikes against targets that the U.S. said included boats attempting to lay mines and missile launch sites, Rubio told reporters on his plane in India's Jaipur that the Strait of Hormuz had to be open "one way or the other".
The war, which began with U.S. and Israeli strikes on Iran on February 28, has caused an unprecedented oil supply shock, pushing up oil prices along with the costs of fuel, fertiliser and food. Iran responded to the strikes by launching drones and missiles at Gulf states that host U.S. bases.
Only a few dozen vessels have been passing through the Strait of Hormuz compared with 125 to 140 daily previously. About a fifth of the world's oil and liquefied natural gas usually flows through the waterway.
Global benchmark Brent crude oil rose almost 3% on Tuesday to $98.91 following news of the U.S. strikes.
'CLOCK CANNOT BE TURNED BACK'
Despite a ceasefire in place since early April, U.S. Central Command said on Monday it had carried out fresh strikes designed "to protect our troops from threats posed by Iranian forces."
Iran's Revolutionary Guards said on Tuesday they reserved the right to retaliate. They said air defence units had downed a U.S. drone and fired at another drone and a fighter jet which they said had entered Iranian airspace over the Gulf region.
In comments posted on his Telegram channel on the occasion of the annual hajj pilgrimage, Iran's Supreme Leader Ayatollah Mojtaba Khamenei said: "The clock cannot be turned back, and the nations and lands of the region will no longer be a shield for American bases."
"From now on, the slogans 'Death to America' and 'Death to Israel' will be the slogans of the Islamic nation and the oppressed people of the world, especially the youth," he added.
U.S. President Donald Trump has previously cited the slogans while justifying military action against Iran. Trump had said talks with Iran were going "nicely" in a lengthy post on Truth Social on Monday, but warned of fresh attacks if they failed. It "will only be a Great Deal for all, or no Deal at all," he wrote.
ABRAHAM ACCORDS PUSH
Trump also called on more Arab and Muslim states including Saudi Arabia to sign up to the Abraham Accords, brokered during his first term in office and aimed at normalising ties between those states and Israel.
Saudi Arabia's longstanding position has been that it would not sign the accords unless there is an agreement on a roadmap to Palestinian statehood.
In another indication of the region's tensions, Israeli Prime Minister Benjamin Netanyahu said on Monday Israel would intensify strikes against the Iran-backed Hezbollah militia in Lebanon.
Israel's military on Tuesday warned residents of the southern Lebanese town of Nabatieh to leave ahead of possible airstrikes.
Israel and Lebanon agreed to a ceasefire in mid-April, but Israel has continued airstrikes it says are acts of self-defence against Hezbollah, which was not party to the truce.
DOHA TALKS
Iranian and U.S. officials have said recent indirect talks have made progress on a memorandum of understanding, or initial deal, that would lead to further negotiations over a final agreement.
Iran's top negotiator Mohammad Baqr Qalibaf, its foreign minister and its central bank governor were in Doha on Monday for talks with Qatar's prime minister on a potential deal, an official briefed on the visit said.
Qalibaf was seeking agreement on the release of around $24 billion of Iranian funds frozen overseas as part of the memorandum of understanding, Iran's Tasnim news agency cited a source close to the negotiation team as saying.
Iran's Fars news agency cited a source saying that the unfreezing of the funds was the last serious sticking point for the memorandum of understanding to be finalised.
According to Iranian sources, an initial deal would cover ending the war on all fronts, establishing a 30-day framework for movement through the Strait of Hormuz, and possibly providing some financial relief - with more complex issues such as Iran's nuclear programme to be negotiated in a second phase.
Iran has been letting some ships through, giving preference to ships linked to countries with which it has alliances or close ties, and striking government-to-government agreements, Reuters has reported.
Trump has said his key aim in the war is to prevent Iran from developing a nuclear weapon with its highly enriched uranium. Tehran has consistently denied it has plans to do that.
(Reporting by Reuters bureaux; Additional reporting by Akanksha Khushi, Doina Chiacu, Ariba Shahid, Hatem Mater, Andrew Mills, Elwely Elwelly, Michael Martina and Parisa Hafezi; Writing by Jan Wolfe, Stephen Coates and Aidan Lewis; Editing by Lincoln Feast and Keith Weir)
