British Prime Minister David Cameron and Iranian President Hassan Rouhani have met on the sidelines of the United Nations General Assembly, the first such meeting since the Iranian revolution in 1979.

A Cameron spokesman said Wednesday the two leaders agreed to seek to progressively improve their bilateral relationship.

Cameron and Rouhani noted the threat posed to the region by the Islamic State militant group and "agreed that all states in the region must do more" to cut support for terrorists groups.

Britain and Iran have recently taken steps to solidify relations.

The spokesman said Cameron and Rouhani agreed it is vital to secure a comprehensive agreement in ongoing negotiations about Iran's nuclear program.