WASHINGTON — The Iraqi government will become more precarious over the next six to 12 months and its security forces have not improved enough to operate without outside help, intelligence analysts conclude in a new National Intelligence Estimate.

Despite uneven improvements, the analysts concluded that the level of overall violence is high, Iraq’s sectarian groups remain unreconciled, and Al Qaeda in Iraq is still able to conduct its highly visible attacks.

“Iraqi political leaders remain unable to govern effectively,” the 10-page document concludes.

The report represents the collaborative judgments of all 16 American intelligence agencies, including the CIA, Defense Intelligence Agency, and the intelligence organization of each military service. It comes at a time of renewed tensions between Washington and Baghdad.

The report says that Iraqi Security Forces, working alongside America, have performed “adequately.” However, it says they haven’t shown enough improvement to conduct operations without American and coalition forces and are still reliant on others for key support.

The findings could provide support for the Bush administration’s argument that coalition forces need to stay in Iraq in order to avoid letting security lapse, should they withdraw from certain areas.

The report predicts that the Iraqi government “will become more precarious over the next six to 12 months” because of criticism from members of Iraqi Shiite parties, Iraq’s top Shiite religious figure Grand Ayatollah Ali al-Sistani, and other Sunni and Kurdish factions.

The assessment also expresses deep doubts that the government of Prime Minister al-Maliki can overcome sectarian divisions and meet benchmarks intended to promote political unity. It finds that Shiite factions have looked at ways to constrain him.

“The strains of the security situation and absence of key leaders have stalled internal political debates, slowed national decisionmaking, and increased Maliki’s vulnerability to alternative coalitions,” the document says.

President Bush had appeared on Tuesday to be distancing himself from the Iraqi leader when he said at a North American summit in Canada: “Clearly, the Iraqi government’s got to do more.”

But an administration official said that, despite the assessment of the limitations of the al-Maliki government, there is no talk at the White House of a need for change in the Iraqi leadership.

The administration believes that anyone would face the same difficulties as Mr. al-Maliki, said the official, who spoke on condition of anonymity so as not to preempt an expected statement from national security adviser Stephen Hadley.