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 claimed this week that he 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 Tehran as part of the coalition they are building to fight the IS militant scourge.
But Kerry said 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."
Tehran is supporting both Iraq and Syria in its battle against IS jihadists.