London, Asharq Al-Awsat—British Prime Minister David Cameron is to meet Iran’s President Hassan Rouhani at the UN in New York this week in a sign of improving relations between the two countries and growing mutual fears of the spread of the Islamic State of Iraq and Syria (ISIS).

The meeting, expected to take place some time during the next two days, will be the first face-to-face encounter between a British and Iranian leader since the 1979 revolution and the foundation of the Islamic Republic.

A source in Cameron’s office told Reuters news agency that the British premier would meet Rouhani on the sidelines of a UN climate summit taking place this week, as part of the latest session of the UN General Assembly.

Cameron is expected to try to enlist Iranian support in the campaign against ISIS in Iraq and Syria.

Though Tehran has denounced ISIS and sent aid to the Iraqi government, it was not invited to a recent international summit in Paris on the Iraq crisis, indicating that the US and its allies were seeking to keep Iran at arm’s length, despite seeking its cooperation.

Reports say Cameron will also press Rouhani to drop Iran’s support for Syrian President Bashar Al-Assad, but is unlikely to succeed.

The two leaders are also expected to discuss the ongoing talks on Iran’s nuclear program, with Cameron likely to resist Iranian attempts to link cooperation on ISIS to concessions in the nuclear talks.

A source in the prime minister’s office told London’s The Guardian newspaper: “We are under no illusion about the dangers of Iran’s nuclear program, and our approach on that is not changing. However, if Iran is willing to join the international community to defeat ISIS then we will work with them on that, but will be clear that you cannot take one approach in Baghdad and another in Damascus.”

“You need a political solution in both if you are serious about defeating ISIS,” the source added.

Cameron and Rouhani’s meeting follows a steady thawing in relations between the UK and Iran, with both states poised to reopen their embassies in London and Tehran.

Britain closed its embassy in Iran in 2011, after it was ransacked by an angry mob.

The meeting between the two leaders also follows the first meeting between UK Foreign Minister Philip Hammond and his Iranian counterpart Mohammad Javad Zarif in New York on Monday.

In a statement issued on Monday, Hammond said: “I met with Foreign Minister Zarif in New York today. We discussed bilateral relations and reaffirmed our commitment to reopen our embassies once the necessary practical arrangements can be made.”

Hammond also said the two men discussed Iran’s approach to human rights and continuing talks on Iran’s nuclear program.

“I was clear with Foreign Minister Zarif that the UK remains committed to securing a deal, but Iran needs to show more realism and flexibility in order for negotiations to succeed,” Hammond added.