US Secretary of State John Kerry warned on Wednesday it will take years for a US-led coalition to defeat the Islamic State group, as Washington said arch-foe Iran had launched its first air strikes against the jehadists. Kerry told the first high-level talks in Brussels of a coalition of around 60 nations that strikes in Iraq and Syria were having a “significant” impact and vowed that they would stay the course. The Pentagon said Iranian F-4 Phantom jets hit IS fighters in eastern Iraq but denied any military coordination with long-term adversary Iran.