Russian Foreign Minister Sergei Lavrov said the United States should cooperate with Syrian President Bashar al-Assad to fight Islamic State and that this required an international coalition uniting all those for whom the jihadists are "a common enemy,” Reuters reports.

Washington currently heads a coalition conducting air strikes on Islamic State in Syria and Iraq and is cooperating with Turkey to provide air cover for rebels inside Syria.

But Moscow has criticized the United States for not working in sync with Syria, an ally of Russia.

In comments to Russia's state TV published by his ministry on Sunday, Aug 9, Lavrov recounted two meetings with U.S. Secretary of State John Kerry amid the recent intensified high-level diplomatic contacts over Syria and fighting the Sunni jihadis.

"Our American partners and some countries in the region persistently refuse to recognize Assad as a partner, which is rather strange," Lavrov said.

"Assad was a fully legitimate partner in destroying chemical arms but somehow he is not in fighting terrorism," he said, referring to a chemical disarmament deal brokered by Moscow and Washington earlier in the conflict.

Lavrov is due to discuss Syria and Islamic State with Saudi Foreign Minister Adel al-Jubeir in Moscow on Tuesday, August 11. The two will also discuss "closer coordination on global energy markets", the Russian ministry said, according to Reuters.

The Russia-proposed coalition, Lavrov said, would "bring together all those already fighting on the ground" who oppose Islamic State. He named the Syrian and Iraqi armies, the Kurds and "the part of the armed opposition that represents Syrians."

"Instead of settling their scores between one another, first one must deal with the common threat, and then seek to agree on how to live in their own country," Lavrov said.