Iraq's prime minister Nuri al-Maliki vowed to uproot al Qaeda in Iraq and said he was sure of victory as his army prepared to launch a major assault against Sunni Islamist militants.
In a televised address on Wednesday, Mr Maliki thanked the international community for its support in the fight against al Qaeda and urged the group to surrender.
Fighters from the al Qaeda affiliated Islamic State of Iraq and the Levant, which is also active across the border in Syria, overran police stations in Falluja and Ramadi cities in Iraq's western Anbar province last week.
The United Nations described the humanitarian situation in Anbar province as critical.
"The situation in Falluja is particularly concerning, as existing stocks of food, water and life-saving medicines begin to run out," UN envoy to Iraq Nikolay Mladenov said in a statement.
The United States is fast-tracking deliveries of military hardware, including drones and missiles, to Iraq, a Pentagon spokesperson said in a statement.
The US promise comes after al Qaeda-linked militants took over parts of Ramadi and Falluja, strategic cities on the Euphrates River.
The US ruled out sending American troops to Iraq, two years after Washington ended nearly a decade of occupation.
Iraqi government forces battling an al Qaeda offensive near the Syrian border launched an air strike on Ramadi city on Sunday killing 25 Islamist militants, according to local officials.
Government officials in western Anbar province met tribal leaders to urge them to help repel al Qaeda-linked militants who have taken over parts of Ramadi and Falluja, strategic Iraqi cities on the Euphrates River.
Al Qaeda's Islamic State of Iraq and the Levant (ISIL) has been steadily tightening its grip in the vast Anbar province in recent months in a bid to create a Sunni Muslim state straddling the frontier with Syria.
Falluja has been held since Monday by Sunni Muslim militants linked to al Qaeda and tribal fighters united in their opposition to Prime Minister Nuri al-Maliki, in a serious challenge to the authority of his Shi'ite-led government in Anbar province.
Al Qaeda's Islamic State of Iraq and the Levant (ISIL) has been steadily tightening its grip in the Sunni-dominated desert province bordering Syria in recent months in a bid to create a Sunni Muslim state straddling the frontier.
But this week's seizure of territory in Ramadi and Falluja was the first time in years that Sunni insurgents had taken control of the region's most important cities and held their positions. In Ramadi, tribesmen and the army have been working together to counter the al Qaeda insurgents.
Iraqi troops trying to retake Anbar province from a mixture of Islamist and tribal foes battled al Qaeda fighters in Ramadi after shelling the western region's other main city, Falluja, overnight, tribal leaders and officials said.
At least eight people were killed and 30 were wounded in Falluja, and residents of both cities said the fighting had limited their access to food, and that they were running low on generator fuel.
Shops were sending food to mosques, and people were being asked through loudspeakers to go to collect it.