WASHINGTON — A senior military commander told a House panel on Thursday that Iraq's security forces are on track to add another 80,000 personnel by the end of the year, but it's a long way from becoming self-sufficient.

Lt. Gen. James Dubik, head of the Multi-National Security Transition Command, said the Iraqi defense minister has stressed to him that the country probably won't assume responsibility for internal security until as late as 2012. Also, it would be unable to defend its borders until at least 2018.

There are "positive signs, indeed, and steps forward, but the truth is that they simply cannot fix, supply, arm or fuel themselves completely enough at this point," Dubik told the House Armed Services Committee.

In private discussions, Dubik said the Iraq defense minister — Abdul-Qader al-Obeidi — continually raises the point that the Iraqis need to buy more air and fire support, helicopters and logistics equipment. These purchases will likely take several years, and training Iraqi soldiers and other personnel on the new equipment will take more time after that, he said.

Rep. Ike Skelton, the Democratic chairman of the panel, said he is worried that U.S. troops will be worn out in the meantime.

"Security in Iraq has improved over the past year, due to the heroic efforts of our troops.... But the question now is how do we sustain it?" Skelton asked.

The training and equipping of Iraqi security forces has long been considered the linchpin in the Bush administration's exit strategy in Iraq. But the public and members of Congress, including many Republicans, have said they want to know there's light at the end of the tunnel.

"I think most Americans would like to have on their refrigerator a chart they can follow that speaks to when we can get out," Rep. Roscoe Bartlett, R-Md.

Dubik responded: "When I talk to my dad about these kinds of things, my advice to him is put no number on the refrigerator."

"Does that mean we'll be there forever?" asked Bartlett. He later noted the U.S. long-term presence in South Korea.

"I don't think people have any stomach for that," Bartlett said.

Dubik said the U.S. has already begun to reduce the number of brigades and will continue to do so as the Iraqis assume more control. But the goal must be not to lose ground, "so that the successes that we fought for, we can retain and leave in such a way that the job is complete," he said.

Iraqi security forces, which now comprise about 500,000 personnel, have grown substantially in the past six months, Dubik said. In the past year, the army has added 55,000 soldiers to its ranks and 15 more combat battalions have given in the lead in combat operations. The national police has grown by 7,500.

"They're in the fight," he said. "They take casualties two or three times of the coalition force."

Still, the burgeoning force remains plagued by numerous issues, including a large absentee rate with 23 percent gone at any one point in time. Also, the Iraqi army lacks enough mid-level officers needed to lead units. Equipment and infrastructure also are lacking, particularly a logistics system that can sustain combat units with such necessities as food and fuel.

In September, an independent panel led by retired Gen. James Jones recommended handing off more combat missions to the Iraqis this year. It also recommended scrapping Baghdad's national police force because of sectarian interests among its members.