Secretary of State John Kerry is planned to travel to Saudi Arabia on Friday and then on to France at the weekend for talks with key US allies on the crisis in Syria.

Secretary of State John Kerry plans to travel to Saudi Arabia on Friday and then on to France at the weekend for talks with key US allies on the crisis in Syria.

The top US diplomat's first stop will be Hafr al-Batin near Saudi Arabia's border with Iraq, where King Salman has just surveyed a major military exercise.

After talks with senior Saudi officials, Kerry will head on to Paris where Foreign Minister Jean-Marc Ayrault will host talks with major western allies.

State Department spokesman Mark Toner said the talks in Saudi Arabia would focus on the crises in Syria and Yemen, both engulfed in civil war.

Ayrault has said that he will meet Kerry and foreign ministers Philip Hammond of Britain, Germany's Frank-Walter Steinmeier and Italy's Paolo Gentiloni.

The talks come at a critical moment in the nearly five-year-old Syrian conflict, with the United Nations planning to relaunch peace talks on Monday.

Saudi Arabia and Washington back some of the opposition factions fighting the Syrian army.

But all four major sponsors are also members of the 17-nation International Syria Support Group, which is pushing both sides to negotiate a truce.