Washington DC - President Donald Trump reportedly blocked an Israeli plan to strike Iranian nuclear sites as Washington attempts to reach a new nuclear deal with Tehran.

The US and Iran, which have not had diplomatic relations for more than 40 years, are seeking a new nuclear agreement after Trump pulled out of a landmark agreement during his first term.

US Special Envoy Steve Witkoff and Iranian Foreign Minister Abbas Araghchi are due to meet in Rome on Saturday, a week after they held the highest-level Iranian-US nuclear negotiations since the collapse of a 2015 accord.

In March, Trump sent a letter to Iran's supreme leader Ayatollah Ali Khamenei urging talks but warning of possible military action if they failed to produce a deal.

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Now, Trump administration officials revealed to the New York Times that Israel had sought Washington's assistance to carry out an attack on Iranian nuclear facilities in May.

According to the paper, the plan and its possible maneuvers were under consideration for months.

But during Prime Minister Benjamin Netanyahu's visit to the White House last week, Trump told the Israelis he would not support an attack. The president instead publicly announced the direct talks with Tehran.

Iran has consistently denied that it is seeking nuclear weapons, but has stepped up its nuclear capacities since Trump scrapped the 2015 agreement.

The latest International Atomic Energy Agency report noted with "serious concern" that Iran had an estimated 274.8 kilograms of uranium enriched to 60%, nearing the weapons grade of 90%.

Israel, meanwhile, has repeatedly tried to involve the US in a potential war against Iran.