Baghadad - US Secretary of State John Kerry arrived in Iraq's capital, Baghdad, as Sunni insurgents keep on expanding their control over towns across North-Western Iraq. In Egypt on Sunday, Kerry warned that Sunni militants Isis' "ideology of violence and repression is a threat not only to Iraq but to the entire region". On Sunday rebels captured border crossings to Syria and Jordan lead by Isis militants even the highly important airport in the northern Tal Afar has also fallen. The town controls the main road from the Syrian border to Mosul, Iraq's second biggest city, which was captured by the rebels two weeks ago. Officials said the rebels of the Islamic State in Iraq and the Levant took two key crossings in Anbar on Sunday, a day after seizing one at Qaim, a town in the province that borders Syria. The capture of Tal Afar airport is a big damage to the government as they were planning to use it as a launch pad to recapture the city of Mosul. Ever since the capture of Mosul in early June, Isis has seized control of large areas in the west and north. They have taken four highly important towns in the predominantly Sunni Anbar province - Qaim, Rutba, Rawa and Anah - in the last two days. Gunmen were said to have captured the border posts of al-Waleed, on the Syrian frontier, and Turaibil, on the Jordanian border, on Sunday after government forces pulled out. The capture of frontier crossings could help Isis transport weapons and other equipment to different battlefields, analysts say. Speaking in Cairo on Sunday, Mr Kerry urged Iraq's leaders "to rise above sectarian motivations and form a government that is united in its determination to meet the needs and speak to the demands of all of their people". Iran's Supreme Leader Ayatollah Ali Khamenei said he opposed any US intervention, and accused Washington of "seeking an Iraq under its hegemony and ruled by its stooges". "The main dispute in Iraq is between those who want Iraq to join the US camp and those who seek an independent Iraq," he said, dismissing talk of sectarianism. The US, which pulled out of Iraq in 2011, is deploying some 300 military advisers to Iraq to help in the fight against the insurgents.