David Cameron is reportedly set to become the first British premier to meet an Iranian President since 1979.
The anticipated meeting between Cameron and Hassan Rouhani will take place in New York.
Cameron's meeting with Rouhani is part of efforts to mobilise support against the Islamic State and drop Iran's support for the Assad regime in Syria, Sky News reports.
The move is seen as the British Prime Minister's attempt to gain active support of regional powers in the Middle East to better combat the Islamic State.
The IS has seized large swaths of territories in Iraq and Syria.
Cameron will also join US President Barack Obama and other members of the UN Security Council to discuss the threat posed by foreign fighters - thought to include hundreds of Britons - engaged in the conflict, the report adds.