The two sides have remained at odds on difficult issues including Iran's nuclear ambitions, Israel's war in Lebanon with the Iranian-backed Hezbollah militia and Tehran's demands for the lifting of sanctions and the release of frozen assets.

Both sides say they have made progress on a memorandum of understanding that would halt the war and give negotiators 60 days to reach a final deal.

Senior Iranian diplomat Hossein Nooshabadi told ISNA news agency on Monday that the possible framework deal included the end of the war on all fronts including Lebanon, the release of blocked Iranian assets, the lifting of the U.S. naval blockade and opening of the Strait of Hormuz, the withdrawal of U.S. forces from the vicinity of Iran and freedom to sell Iranian oil. (Reuters)

HORMUZ AND GULF BLOCKADE - Tehran sees its control of Hormuz and Washington views its blockade of Iranian ports as their chief points of leverage.

NUCLEAR - The United States believes Iran wants to build a nuclear bomb. Iran has always denied this, saying its atomic programme is for peaceful purposes only. The focus is on its enrichment of uranium, which generates fuel for nuclear power but can also make material for a warhead. An agreement may eventually be possible including a lengthy moratorium on enrichment and the export or dilution of the stockpile.

BALLISTIC MISSILES - A main U.S. demand before the war was that Iran limit the range of its ballistic missiles so that they could not reach Israel. Iran has always refused to discuss its ballistic missiles, saying its right to conventional weapons cannot be on the table and that it still has a large arsenal. 

SANCTIONS AND FROZEN ASSETS - Iran's economy has been hurt by sanctions for years, contributing to the nationwide unrest in January. Tehran badly needs them to be lifted and tens of billions of dollars of Iranian oil revenues frozen in foreign banks to be released. It also wants reparations for war damage. (Reuters)

Iran's foreign ministry spokesperson said on Monday that conclusions have been reached on many topics discussed in a potential 14-point memorandum of understanding, but this does not mean a deal to end the Middle East war is imminent.

The framework is focused on an end to the war and a U.S. naval blockade in exchange for Tehran taking steps to ensure safe transit in the Strait of Hormuz, said the spokesperson, Esmaeil Baghaei.

If Iran's Supreme National Security Council approves the memorandum of understanding, it will then be sent to the country's supreme leader for final approval.

The U.S. understood Supreme Leader Ayatollah Mojtaba Khamenei had endorsed the broad template of the deal, the senior U.S. official said.

If the first phase of the agreement progressed, the nuclear issue could be reviewed and negotiated during the 60-day period, Baghaei and Nooshabadi said.

U.S. Secretary of State Marco Rubio spoke of entering into a "very real, significant, ​time-limited negotiation on the nuclear matter" during the 60 days.

The last deal over the nuclear programme - struck in 2015 and torn up by U.S. President Donald Trump in 2018 - took years of negotiations between large teams of technical experts. (Reuters)

Tehran is yet to respond to the latest US strikes, and it remains unclear if the new American agression will have any impact on a potential peace agreement between the two warring nations.

Israel's Prime Minister Benjamin Netanyahu said he and Trump had agreed that "any final agreement with Iran must eliminate the nuclear threat entirely".

Oil prices have risen after the US conducted new strikes on Iran, threatening an already fragile ceasefire that began April 8.

Brent futures increased by more than 1% in early Asian trade to $97.32 a barrel. US West Texas Intermediate crude was up slightly from Monday's last traded price but down 5.5% from Friday's close.

Donald Trump has said he expected Iran to hand over its enriched uranium to the United States to be destroyed or have it destroyed in Iran with an international witness as the American forces conducted "self-defence" strikes on Iranian boats and missile launch facilities.

"The Enriched Uranium (Nuclear Dust!) will either be immediately turned over to the United States to be brought home and destroyed or, preferably, in conjunction and coordination with the Islamic Republic of Iran, destroyed in place or, at another acceptable location, with the Atomic Energy Commission, or its equivalent, being witness to this process and event," he said in a social media post.

Iran's top negotiator and its foreign minister were in Doha for talks with Qatar's prime minister on a potential deal with the U.S. to end the three-month-old war, an official briefed on the visit said on Monday, after Washington and Tehran played down hopes for an imminent breakthrough.

The official briefed on the Iranians' Doha visit told Reuters the discussions focused primarily on the Strait of Hormuz and Iran's stockpile of highly enriched uranium while Iran's central bank governor attended to discuss the potential release of frozen Iranian funds as part of a final deal.

Iran's foreign ministry spokesperson Esmaeil Baghaei said earlier that nuclear issues would only be negotiated on if the framework accord is agreed first.

American forces have launched new strikes on missile sites in southern Iran and boats trying to lay mines, US Central Command (CENTCOM) said, as top Iranian negotiators arrived in Doha for talks to end the three-month-old war. "US forces conducted self-defence strikes in southern Iran today to protect our troops from threats posed by Iranian forces," Tim Hawkins, a CENTCOM spokesman, said in a statement.

It gave no details of the attacks and said only that the targets included missile launch sites and boats trying to "emplace mines."

The strikes threatened an already fragile ceasefire that began April 8 as the United States and Iran struggle to reach an accord to end a war that has rattled the global economy with a severe disruption of energy flows.