WASHINGTON -- Although U.S. and Iraqi officials say Iraqi security forces have made progress, top American generals said Thursday they could not commit to how self-sufficient the Iraqi forces must be before the U.S. can pull out of the country completely.

“Even as our combat roles go down, our enabling roles will continue for some time,” Army Lt. Gen. James Dubik, commanding general of the Multi-National Security Transition Command in Baghdad, told the House Armed Services Committee. “The truth is that they cannot fix, supply, arm or fuel themselves completely enough at this point.”

Iraqi Defense Minister Abdul Qadir said earlier this week that Iraq might be able to handle its internal security by the start of next year and external security by 2018.

But the U.S. military is making its judgments on 90-day cycles, Lt. Gen. Ray Odierno, commander of Multinational Corps in Iraq, said in a video conference from Iraq.

During Dubik’s appearance before the Armed Services Committee, members pressed him for a troop withdrawal timeline.

“Most Americans would like to know that someday our presence would no longer be needed,” Rep. Roscoe Bartlett R-Md. said. “Americans would like to have a chart on their refrigerator that looks to when we can get out.”

Dubik responded: “Put no number on the refrigerator.”

Before they can go it alone, Iraqis need to cut police corruption and develop support systems such as doctors and mechanics for combat troops, Dubik said.

The U.S. eventually will scale back its combat forces even if it keeps a presence in Iraq, said Dubik, using as examples the noncombat U.S. troops helping keep the peace in many countries around the world.

Although declining to offer a specific date for when that transition might occur in Iraq, Dubik said Iraqi ground forces are the best they’ve been – with more troops and better training.

 Iraqis are getting fed up with extremists and taking interest in paid positions in the Concerned Local Citizens program, he said, and Iraqi security forces have taken control of security in nine of 18 provinces in Iraq. Dubik predicted that the Iraqi forces will grow from  about 500,000 personnel now to 580,000 by the end of the year.

“There’s a strong temptation to look at these numbers of Iraqi forces and ask why they cannot fully shoulder the burden of combating insurgents and terrorists within Iraq’s borders,” Rep. Jim Saxton R-N.J. said. “Yet we must remember the unique challenges faced by the government of Iraq.”