King Salman of Saudi Arabia is to meet President Barack Obama in Washington, on his first trip to the United States since assuming the throne in January, BBC News reports.

The meeting comes amid a period of strained bilateral relations.

The king is expected to reiterate the concern of Gulf states over the recent deal on Iran's nuclear programme.

They fear that lifting sanctions could allow Iran to extend its support for militant groups and actions across the region they consider destabilising.

Obama is expected to press King Salman to ensure humanitarian organisations are given unrestricted access to Yemen, where the Saudis are leading a coalition against the Houthi rebel movement.