Washington’s arch-foe Iran has a role to play in tackling Islamic State militants who have overrun large swathes of territory in Iraq and Syria, US Secretary of State John Kerry said.

Iran’s supreme leader Ayatollah Ali Khamenei said this week that his government had rejected a request from the United States for cooperation on the battlefield.

US officials have not confirmed or denied making an offer in private, but they do not regard Iran as part of the coalition they are building to fight the IS militant scourge.

Kerry said Friday that in combating the jihadist threat “there is a role for nearly every country to play, including Iran.”

Just last week, the top US diplomat had said it would be inappropriate to invite Iran to meetings seeking to building an international coalition because of Tehran’s “engagement in Syria and elsewhere.”

Iran is actively supporting Iraq’s government against IS jihadists, and  helping Syria in its battle against both the IS group and unaffiliated rebel groups.

Washington has struggled with its anti-IS engagement in Syria, already in the grips of a brutal civil war pitting the rebels against the forces of President Bashar al-Assad.

Speaking before a group of 35 countries brought together for a meeting at the UN Security Council by top US diplomat John Kerry, Iran’s deputy foreign minister, Abbas Araghchi, stressed the need to cooperate with governments in the region.

“In order to fight IS in Iraq and Syria, we must cooperate with the governments of those countries,” he said.