Shifting the U.S. military mission in Iraq to only combat support and terror-fighting will wipe out most of the achievements made in the last three years, warns the latest National Intelligence Estimate released Thursday.

That dire prediction, buried deep within the unclassified version of the report, states:

"We assess that changing the mission of coalition forces from a primarily counterinsurgency and stabilization role to a primary combat support role for Iraqi forces and counterterrorist operations to prevent AQI (Al-Qaeda in Iraq) from establishing a safe haven would erode security gains achieved thus far," the report states.

The NIE also concludes that Iraq's internal political struggles, ongoing sectarian violence and terror threats leave the country in a precarious situation for the next six-12 months.

The unclassified version of the report also points out that Iraq's security has faced "measurable but uneven improvements" since January.

• Click here to read the new National Intelligence Estimate on Iraq.

The report — the collective judgments of the 16 U.S. intelligence agencies, including the CIA, Defense Intelligence Agency and the intelligence organization of each military service — sparked more heated exchanges in Washington as lawmakers position themselves for an impending progress report on Iraq from Gen. David Petraeus, head of Multinational Forces in Iraq.

Anti-war lawmakers have suggested that U.S. troops should redeploy and perform only counter-terror and combat support operations, as recommended by the ISG in its 2005 report.

"This report is further evidence that there is a disconnect between military operations to establish security in Iraq and elsewhere in the country and the willingness of an Iraqi political leadership to take advantage of improved security to promote political compromise and reconciliation on behalf of all Iraqis," said Sen. Chris Dodd, D-Conn., a 2008 presidential contender.

The assessment also comes at a time of renewed tensions between Washington and Baghdad -- tensions that President Bush tried to ease on Wednesday by offering explicit support to Nouri al-Maliki after heavy criticism of the prime minister from Senate Armed Services Committee chairman Carl Levin.

The NIE report presents a picture of a glass either half-full or half-empty. The 10-page document, with only four pages of actual findings, concludes that "the steep escalation of rates of violence has been checked for now, and overall attack levels across Iraq have fallen during seven of the last nine weeks. Coalition forces, working with Iraqi forces, tribal elements, and some Sunni insurgents, have reduced Al Qaeda in Iraq’s (AQI) capabilities, restricted its freedom of movement, and denied it grassroots support in some areas."

The report continues that despite those achievements, "the level of overall violence, including attacks on and casualties among civilians, remains high; Iraq’s sectarian groups remain unreconciled; AQI retains the ability to conduct high-profile attacks; and to date, Iraqi political leaders remain unable to govern effectively."

"AQI no longer enjoys the same freedom of movement they did six months ago particularly in Anbar province as well as other areas of the cournty....AQI is losing leaders at a great clip. Their ability to intimidate and elicit popular support is decreasing."

The assessment also states that the Iraqi Security Forces are performing adequately, but have not improved enough to conduct major operations without the coalition for logistics and combat support.

The report expresses deep doubts that al-Maliki's government 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 decision-making, and increased Maliki's vulnerability to alternative coalitions," the document says.

"Any leader, not just Maliki, would face significant challenges from these groups around such sensitive national issues," said a senior intelligence official who briefed reporters on the NIE.

The official also noted that the sects are starting to perceive that the U.S. will eventually draw down troops and that is playing a factor in their decision-making and efforts to position themselves to "take advantage of or protect against the consequences."

FOX News' Trish Turner and The Associated Press contributed to this report.