Iran's supreme leader condemned US intervention in Iraq yesterday, accusing Washington of seeking control as Sunni insurgents drove toward Baghdad from the Syrian border and consolidated positions in the north and west.
Meanwhile, US Secretary of State John Kerry on a surprise Egypt visit yesterday urged Iraqi leaders to rise above "sectarian considerations", and said Washington was "not responsible" for the crisis there.
The statement by Ayatollah Ali Khamenei was the clearest statement of opposition to a US plan to dispatch of up to 300 military advisers in response to pleas from the Iraqi government and runs counter to speculation that old enemies Washington and Tehran might cooperate to defend their mutual ally in Baghdad.
"We are strongly opposed to US and other intervention in Iraq," IRNA news agency quoted Khamenei as saying. "We don't approve of it as we believe the Iraqi government, nation and religious authorities are capable of ending the sedition."
The Iranian and the US governments had seemed open to collaboration against al-Qaeda offshoot the Islamic State in Iraq and the Levant (ISIL), which is fighting both the US-backed, Shia-led government of Iraq and the Iranian-backed president of Syria, whom Washington wants to see overthrown.
"American authorities are trying to portray this as a sectarian war, but what is happening in Iraq is not a war between Shia and Sunnis," said Khamenei, who has the last word in the Islamic Republic's Shia clerical administration.
Accusing Washington of using Sunni Islamists and followers of ousted Iraqi leader Saddam Hussein, he added: "The US is seeking an Iraq under its hegemony and ruled by its stooges."
Tehran and Washington have been shocked by the lightning quick offensive, spearheaded by ISIL, that has seen large swathes of northern and western Iraq fall to the hardline extremist group and other Sunni fighters since June 10, including the north's biggest city Mosul.
ISIL thrust east from a newly captured Iraqi-Syrian border post yesterday, taking three towns in Iraq's western Anbar province after seizing the frontier crossing near the town of Qaim on Saturday, witnesses and security sources said.
The gains have helped ISIL secure supply lines to Syria, where it has exploited the chaos of the uprising against President Bashar al-Assad to seize territory.
The fall of Qaim represented another step towards the realisation of ISIL's military goals, erasing a frontier drawn by British and French colonial map-makers a century ago.
The government said its forces had made a "tactical" withdrawal from the towns to allow troops to regroup and retake the areas.