US and Iranian officials are due to meet today for crunch talks, as Iran's foreign minister warns that the US could trigger a 'devastating war'

Iran's foreign minister has warned the US could unleash a "devastating war" on the "whole region" as tensions mount between the two countries.

US and Iranian officials are due to meet today for crunch talks, with President Donald Trump threatening to strike Iran if a nuclear deal is not reached. The negotiations, which will be indirect and mediated by Oman in Geneva, come amid the largest US military build-up in the Middle East since the brutal US-led invasion of Iraq in 2003.

"There would be no victory for anybody - it would be a devastating war," Iranian Foreign Minister Abbas Araghchi told India Today in an interview filmed on Wednesday just before he flew to Geneva.

"Since the Americans' bases are scattered through different places in the region, then unfortunately perhaps the whole region would be engaged and be involved, so it is a very terrible scenario."

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Araghchi is set to sit across from US Special Envoy Steve. The pair held multiple rounds of talks last year that collapsed after Israel launched its 12-day war against Iran in June.

In this third round of talks, Trump is pushing for a complete halt to Iran's enrichment of uranium, as well as limits to the country's ballistic missile programme and its support of regional militant forces. Iran has insisted the talks must remain focused solely on nuclear issues.

US Secretary of State Marco Rubio said on Wednesday that Iran is "always trying to rebuild elements" of its nuclear programme, adding that while Tehran is not enriching uranium right now, "they’re trying to get to the point where they ultimately can".

Iran says it has not enriched uranium since US forces bombed its three key nuclear sites in June. Tehran, party to the Non-Proliferation Treaty, maintains that it has the right to enrich uranium for civilian purposes but denies ever seeking nuclear weapons.

The International Atomic Energy Agency (IAEA) says its inspectors have been prevented from visiting the three sites hit, but have inspected all 13 declared nuclear facilities that were not targeted.

The Associated Press reports that satellite photos show activity at two of the three key sites, leading to concerns that Iran may to be trying to recover material.

Araghchi met Oman's Foreign Minister Badr al-Busaidi in Geneva on Wednesday night. The men "reviewed the views and proposals that the Iranian side will present to reach an agreement on the Iranian nuclear programme, based on the guiding principles agreed upon in the previous round of negotiations," the state-run Oman News Agency reported.

Al-Busaidi will pass Iran's proposal to US officials on Thursday, the report added.

The West and the IAEA say Iran operated a nuclear weapons programme until 2003 and that, up until the attack in June, it had been enriching uranium to 60 per cent purity - close to the 90 per cent level considered "weapons-grade". Western powers argue there is no credible civil justification for Iran's enrichment of uranium to high levels.

The prospect of US military action and Iranian retaliation against the American-allied countries in the region has heightened fears of a wider conflict. Oil prices have risen in recent days amid the uncertainty, with benchmark Brent crude now at about $70 a barrel.

All American vessels, typically docked in Bahrain, appear to be out at sea, according to satellite images taken on Tuesday and Wednesday by Planet Labs PBC.