Iraq crisis: Islamic State weakened by US airstrikes, claims Pentagon

But the department warned the group are still potent

U.S. F/A-18 fighter jets take off for mission in Iraq from the flight deck of the U.S. Navy aircraft carrier USS George H.W. Bush, in the Persian Gulf, Monday, Aug. 11, 2014. (AP Photo/Hasan Jamali)

US airstrikes in Iraq last week have slowed the advance of Islamic State militant group, the Pentagon said on Monday.

But the department added its strikes were unlikely to substantially weaken the al-Qa'ida offshoot formerly known as Isis, which swept into northern Iraq in a stunning advance in June.

"We assess that US airstrikes in northern Iraq have slowed ISIL's [Isis] operational tempo and temporarily disrupted their advances toward the province of Arbil which includes the capital of Iraq's semiautonomous Kurdish region", said Army Lieutenant General William Mayville Jr., a senior Pentagon official.

"However, these strikes are unlikely to affect ISIL's overall capabilities or its operations in other areas of Iraq and Syria," Mayville told reporters at the Pentagon.

Last week, the White House said it would carry out airstrikes in Iraq in an attempt to protect its personnel working in the Kurdish city of Arbil, and to ensure that northern Iraq's minority Yazidis were not subject to systematic violence at the hands of the extremist Sunni militants.

But Mayville added the Islamic State, was still a threat. "[The group] remains focused on securing and gaining additional territory throughout Iraq and will sustain its attacks against Iraqi and Kurdish security forces and their positions, as well as target Yazidis, Christians, and other minorities," he said.

The 15 airstrikes carried out so far are the first direct US military action in Iraq since the Obama administration completed its withdrawal of US troops at the end of 2011 - hoping to mark an end to the long, bloody US military involvement in the country.

Futher deepening US military involvement in Iraq, US government sources announced in a separate statement on Monday that it would be directly supplying weapons to Peshmerga forces from Iraq’s semiautonomous Kurdish region.

Peshmerga personnel have been battling to stem advances by Islamic State militants, after the group stormed Iraq’s second city, Mosul, on 10 June, causing the Iraqi army to flee.

The officials declined to specify when the supply program began or what sort of arms it included.

The US announcements came as Iraq’s new President appointed Haider al-Abadi as the Prime Minister, making it unlikely that Nouri al Maliki will serve a third term in the position. It is now feared the change will raise the possibility of civil conflict in Baghdad.

Additional reporting by agencies