(Adds Iran comment, Russian comment, U.N. comment) By Michelle Nichols and Louis Charbonneau United NATIONS, Sept 19 (Reuters) - U.S. Secretary of State John Kerry said on Friday that Iran had a role to play in a global coalition to tackle Islamic State militants who have seized swaths of Iraq and Syria and proclaimed a caliphate in the heart of the Middle East. "The coalition required to eliminate ISIL (Islamic State) is **t only, or even primarily, military in nature," Kerry told a United Nations Security Council meeting on Iraq. ...