US Secretary of State John Kerry has landed in Baghdad for high-level talks with Iraq's new prime minister and its government that is supposed to fight against a Sunni Islamist insurgency in the north and west of the country.

Kerry hailed the formation of an inclusive coalition under Prime Minister Haider al-Abadi, who took over from controversial Shiite politician Nouri al-Maliki, as a "major milestone". Washington had said that the formation of an inclusive Iraqi government was a precondition for expanded support to Baghdad against Isis (now known as Islamic State).

A senior state department official said that Iraq will have a "critical role" in the effort to "degrade and ultimately eventually defeat" Isis.

Baghdad is the first stop for Kerry on his Middle East trip aimed at building support against Isis. He will meet Jordan's King Abdullah II and will travel to Saudi Arabia to meet Saudi and other Arab officials to discuss how to defeat the jihadists in Syria and Iraq.