The global chess game linking Russia's war in Ukraine and the Iran nuclear deal

Russia has attempted to use its support for reviving the Iran nuclear deal as leverage to minimise sanctions over its invasion of Ukraine.

The overlapping diplomatic crises have drawn in nations from around the world with a range of complicated relationships and agendas.

Here is what each of the main players want from each other and why.

United States

The Biden administration desperately wants to revive the so-called JCPOA (Joint Comprehensive Plan of Action) Iran nuclear deal, from which Donald Trump withdrew in 2018.

That would see sanctions lifted on Iran in return for curbs on its nuclear programme.

For the US it would mean Iranian oil back on the market as the energy crisis caused by sanctions on Russia over its invasion of Ukraine unfolds.

The US is still "continuing to engage" with Russia about the Iran deal despite the Ukraine war, according to officials.

However, it has made clear it will not accede to Russian demands to be allowed to continue a full trading and investment relationship with its ally Iran.

Instead, it will allow Russia to continue providing equipment to Iran’s nuclear power plant at Bushehr, as the original 2015 Iran nuclear deal allowed.

UK and Europe

The UK, France and Germany - the so-called E3 - have been working hard to restore the nuclear deal with the "utmost urgency" to stop Iran getting a nuclear bomb.

They have accused Moscow of seeking to exploit the nuclear deal negotiations in Vienna to escape from some sanctions imposed over Ukraine, "risking the collapse of the [Iran] deal.”

Sanctions on Russian oil leave an energy gap to be filled so the E3 are keen to see the return of Iranian oil following the establishment of a new nuclear deal.

Boris Johnson will also hold talks with Saudi Arabia and the United Arab Emirates as he seeks to end the "addiction" of the West to Russian oil and gas.

That effort is being coordinated with the US.

Russia

On Tuesday, Sergey Lavrov met in Moscow with his Iranian counterpart and ally Hossein Amirabdollahian.

Mr Lavrov said it was untrue that Moscow was blocking efforts to revive the Iran nuclear deal, and that the final points were being "polished".

He also said he had received "written guarantees" from the US that sanctions against Moscow over Ukraine would not hinder cooperation within the framework of the Iran deal, allowing Russia to continue nuclear business with Iran.

Russia's closeness to Iran appeared to have helped smooth things along for the nuclear deal.

Meanwhile, Russia continues to demand "security guarantees" from Europe and the US against Nato expanding eastwards.

Iran

Tehran is keen to get sanctions lifted with a revived nuclear deal, allowing it to massively boost oil exports.

That would happen at a time when its ally Russia is unable to export to European countries that have sanctioned it over Ukraine.

Iran would be able to fill the gap for those countries.

It has defended Russia over the nuclear deal saying that Moscow had "not caused any obstruction" and would continue to play a "very positive, constructive role".

However, Iran is also keen for guarantees from the US that a future American president would not withdraw from a revived nuclear deal.

In a related development, on Wednesday Iran released two British-Iranians, Nazanin Zaghari-Ratcliffe and Anousheh Ashouri, who had been detained by Tehran for six and five years respectively.

Their fate had been linked to an outstanding £400 million debt owed by the UK. On Wednesday, Foreign Secretary Liz Truss said the UK has settled that in a way which complied with UK and international sanctions.

Saudi Arabia and the UAE

Saudi Arabia is suddenly very popular as Western countries face a lack of Russian energy.

In addition to Mr Johnson's visit, Mr Biden is keen for the kingdom to pump more oil and keep the global price down.

However, relations between the US and Saudi Arabia, which Mr Biden has called a "pariah", are at a low ebb.

Meanwhile, the United Arab Emirates and Israel, America's close ally, have been lobbying the US for a new Middle East security strategy involving more missile defence and sharing of intelligence.

They believe if the Iran deal is revived then Tehran could use its increased oil revenue to fund violent groups across the Middle East.

Qatar’s Foreign Minister Sheikh Mohammed bin Abdulrahman Al Thani is talking to everyone.

He spoke with his Iranian counterpart on Saturday, and then with with US Secretary of State Antony Blinken.

He is expected in Moscow on Sunday to discuss both the nuclear deal and Ukraine with Mr Lavrov.