Sep 30, 7:55 PM EDT

By ROBERT BURNS

AP Military Writer

WASHINGTON (AP) -- Sunni Arab opposition to Iraq's draft constitution has increased the potential for instability and called into question U.S. hopes for substantial troop cuts next spring, the top U.S. commander in Iraq said Friday.

Gen. George Casey, speaking at a Pentagon news conference with Defense Secretary Donald H. Rumsfeld, said his prediction in July that "fairly substantial" troop withdrawals could begin next spring was based on a key assumption: that satisfactory progress on the political and security fronts would continue.

"Now this constitution has come out, and it didn't come out as the national compact that we thought it was going to be," he said.

"And there's division there ... and that caused the situation to change a little bit," Casey said.

Indeed, violence in Iraq has increased as Sunni insurgents strike at Shiites and try to undermine the October voting on the proposed constitution. At least 200 people have been killed in the past five days, including 13 U.S. service members.

There are now about 149,000 U.S. troops in Iraq. Casey noted that he had told Congress on Thursday that even with the new uncertainty he still believed some troop reductions were possible in 2006.

In Princeton, N.J., on Friday, Secretary of State Condoleezza Rice made a rare reference to the number of U.S. troops killed in Iraq - nearly 2,000 - but said the U.S. must not abandon its mission there.

"In a world where evil is still very real, democratic principles must be backed with power in all its forms," Rice said. "Any champion of democracy who promotes principle without power can make no real difference in the lives of oppressed people."

Rumsfeld pounds the podium while defending the skill of Iraqi security forces.

Documents

Proposed Iraqi Constitution (Full Text)

Key Findings on WMD

Interactives

Surviving the Sand

Governing Iraq

Prison Abuse Scandal

1,500 U.S. Deaths

Street Fighting

Coalition Casualties

Recent Stories

Bombings Kill 110 Shiites Over Two Days

U.S. Commander Now Doubts Troop Cutbacks

A List of Major Attacks Targeting Shiites

A Look at U.S. Military Deaths in Iraq

Major Developments in Iraq on Thursday

Five U.S. Soldiers Killed by Roadside Bomb

Three Car Bombs Kill 40 North of Baghdad

PHOTO GALLERY

Iraq

In Iraq, the Sunni Arabs who ran the country under former President Saddam Hussein but represent a minority of the population, boycotted last January's elections and thus had a smaller voice in the drafting of the constitution.

Sunni leaders have urged their followers to reject the constitution, saying it would leave them weak compared to the Shiites and Kurds who were repressed under Saddam. U.S. Ambassador Zalmay Khalilzad has been struggling to negotiate changes to the charter in hopes of winning Sunni support.

Senior U.S. officials, including Rumsfeld and Casey, have said they expect the draft constitution to be approved in an Oct. 15 national referendum, even if the Sunni Arabs vote against it in large numbers. Casey said in congressional testimony Thursday that it was "entirely possible" that a strong Sunni vote against the constitution would deepen the political divisions, although he did not link that to prospects for U.S. troop withdrawals.

The constitution, if approved, would form the basis for elections in December of a permanent Iraqi government.

Sen. Carl Levin, D-Mich., said Thursday that if the Iraqis do not reach a political accommodation by the end of the year the Bush administration should consider a timetable for the withdrawal of American forces. He stressed that this did not mean setting a date for departure "at this time," but would let the Iraqis know they did not have an unlimited time to settle their differences.

"We can't stay for an unlimited time, due to the strain on our forces," Levin said.

One of the keys to eventually bringing all American troops home from Iraq is training and equipping enough Iraqi soldiers and police to defend the country by themselves. Casey raised some eyebrows in Congress on Thursday when he disclosed that only one Iraqi army battalion was ready to go into combat without U.S. support. A few months ago three battalions were thought to have that capability. Casey said Friday he was not certain why the number fell from three to one but it might be linked to a shake-up in battalion leaders.

Whatever the case, Casey argued, the more important fact is that more than 30 Iraqi army battalions are deemed capable of leading a combat operation against the insurgents, even if they require U.S. support.

"Next year at this time, I'll be much more concerned about it" if only a small number of Iraqi battalions are still considered battle-ready by American officers, Casey said.

Casey and Rumsfeld appeared before reporters at the Pentagon at the conclusion of a week in which the Bush administration forcefully pressed its case for continued patience among the American public, which polls indicate is becoming more troubled by the daily U.S. casualties in Iraq and uncertain prospects for victory.

Casey and Gen. John Abizaid, the Central Command commander who has overall responsibility for military aspects of the global war on terrorism, briefed several congressional committees - in private and in public - and Rumsfeld painted a picture Friday of the insurgencies in Iraq as well as Afghanistan giving ground.

"The enemy is losing," he said.

Casey predicted that violence would continue in Iraq as the Oct. 15 referendum approaches.

"To be sure, the next months will be difficult, as our enemies also recognize what's at stake. They are already challenging the referendum process with increased terror attacks to create the impression that attempts of progress are futile and that Iraq can never become a modern democratic society. They are attacking the will of the Iraqi people and they are attacking the will of our coalition publics. They are failing in Iraq."