WASHINGTON (AFP) - The United States has discussed the threat posed by Islamic State (IS) militants with envoys from its traditional foe Iran on the sidelines of nuclear talks, the State Department revealed Friday.

"Discussion on this threat did arise on the margins of the meeting as they have from time to time," spokesman Jeff Rathke told reporters.

But he stressed the meetings were "focused primarily on nuclear issues."

Iran and global powers resumed full talks on Friday as they seek to hammer out a comprehensive nuclear deal by a November 24 deadline.

But US and Iranian teams held bilateral meetings on Wednesday and Thursday as they seek to narrow large gaps on some of the thorniest issues to rein in Iran's suspect nuclear programme.

US Secretary of State John Kerry on Monday ruled out military cooperation with Iran, but said Washington remained open to talks with Teheran about the threat posed by the Islamic State group.

Iranian Foreign Minister Mohammad Javad Zarif this week reiterated Iran's disappointment that it was not invited to join Paris talks on the IS crisis as the US seeks to build a coalition to defeat the militants who have captured a large swathe of territory in Iraq and Syria.

Mr Kerry was Friday chairing a meeting of the UN Security Council in New York, at which Iran has asked to speak.