The sharp criticism of Prime Minister Nuri al-Maliki came as he scrambled to repel an insurgent onslaught that has seen an entire province and parts of three others fall out of government control in an offensive that could threaten Iraq's very existence.
The militants' swift advance has sparked international alarm and the United Nations has warned that the crisis was "life-threatening for Iraq".
Hundreds of thousands of Iraqis have been displaced in the nine days of fighting and an unknown number killed, while dozens of Indians and Turks have been kidnapped.
With President Barack Obama mulling a request by Baghdad for air strikes on the advancing militants, US officials castigated Maliki, publicly echoing long-held criticisms among his domestic opponents of sectarianism.
US Vice President Joe Biden urged greater political inclusion in Iraq in phone calls with Maliki and other Iraqi officials, the White House said.
Biden "stressed the need for national unity in responding to the ISIL threat against all Iraqi communities," in calls with Maliki, Iraqi Council of Representatives Speaker Osama al-Nujaifi, and President of the Iraqi Kurdistan Region Masoud Barzani, it said.
The top-ranking military officer, General Martin Dempsey, and former US commander David Petraeus both also rounded on the premier.
"There is very little that could have been done to overcome the degree to which the government of Iraq had failed its people," Dempsey said.
Petraeus warned at a conference in London that Washington risked becoming an "air force for Shiite militias" and supporting "one side of what could be a sectarian civil war" if political reconciliation were not agreed.
The remarks came after Iraqi Foreign Minister Hoshyar Zebari told reporters in Saudi Arabia that Baghdad had asked Washington "to conduct air strikes against terrorist groups".
Zebari acknowledged "the need for drastic political solutions."
Washington has deployed an aircraft carrier to the Gulf and sent military personnel to bolster security at its Baghdad embassy, but Obama insists a return to combat in Iraq is not in the cards.

Indian telecom operator Idea Cellular has announced the launch of a new smartphone in its ID line-up. Dubbed as ID 4000, the smartphone comes with dual-SIM support and will go on sale in 11 telecom circles, where Idea offers 3G services.


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