TEHRAN - Japanese Prime Minister Shinzo Abe is heading to Iran with a keen eye on international sanctions and domestic politics.

The visit, which begins Wednesday, is partly aimed at easing tensions between Washington and Tehran over Iran's nuclear programme.

However, observers have expressed doubt over what can actually be achieved.

For Mr Abe, the trip might help boost his image as a global statesman ahead of elections back home, experts say.

Mr Abe will be the first Japanese prime minister to visit Iran in four decades, and is expected to hold talks both with Supreme Leader Ayatollah Ali Khamenei and President Hassan Rouhani.

Officially, Japan and Iran are marking the 90th anniversary of their diplomatic relationship this year.

Much more significant is that the trip comes shortly after US President Donald Trump made a state visit to Japan.

And US relations with Iran have nosedived over Washington's withdrawal from a 2015 nuclear deal over Iran's nuclear programme.

Tensions escalated further when the US sent an aircraft carrier to the region, raising fears of an actual confrontation.

So there are hopes that Mr Abe might be able to engage in some shuttle diplomacy between the two sides, dialling down tensions and getting them to talk to each other.

Just one day before heading off, the Japanese prime minister spoke to Mr Trump on the phone and exchanged views on Iran, a spokesperson for Mr Abe told reporters on Tuesday.

Essentially, in 2015 Iran agreed to limit its nuclear programme in return for sanctions being lifted.

The deal was done under the Obama administration though, and Mr Trump withdrew from it last year.

The US reinstated unilateral sanctions while other signatories to the 2015 deal - like the EU, Russia and China - still hope to keep the agreement alive.(FA)