BAGHDAD — Iraq's top army officer warned on Wednesday that a pullout of all US troops by the end of 2011 was premature as the White House insisted it was on track to end combat operations this month as planned.

Lieutenant General Babaker Zerbari said American forces may be needed in the conflict-wracked nation for a further decade, in comments that called into question Washington's policy of a phased and "responsible drawdown."

The general's remarks, which could irk political leaders in Baghdad, came after eight of his soldiers were killed in a brazen attack that exposed shaky security here less than three weeks before US troop numbers fall to 50,000.

"At this point, the withdrawal (of US forces) is going well, because they are still here," Zebari told AFP on the sidelines of a defence ministry conference in Baghdad.

"But the problem will start after 2011 -- the politicians must find other ways to fill the void after 2011.

"If I were asked about the withdrawal, I would say to politicians: the US army must stay until the Iraqi army is fully ready in 2020."

There are now 64,000 American soldiers in Iraq, but this number is due to fall by 14,000 by the end of the month when the United States is set to declare an end to combat operations and switch to a training and advisory mission.

All American troops must leave Iraq by the end of next year, according to the terms of a bilateral security pact, and President Barack Obama has insisted that the ongoing withdrawal is on schedule and will not be altered.

White House spokesman Robert Gibbs reiterated Washington's determination to stick to its plans, telling reporters the US was "on target by the end of the month to end our combat mission" in Iraq.

Also in Washington, Obama convened his national security team to discuss Iraq, with about 20 senior civilian and military officials in attendance.

The threat to Iraqi security forces was shown on Wednesday in the central town of Saadiyah, where insurgents lured troops into a booby-trapped house, killing the eight soldiers in co-ordinated blasts that marked the start of Ramadan when violence tends to surge.

The decaying bodies of three civilians killed more than a week ago were also found under the rubble of the building, a doctor said.

Gunmen initially opened fire on an army checkpoint at around 5:00 am (0200 GMT) in Saadiyah, 100 kilometres (62 miles) northeast of Baghdad, before fleeing into a nearby house, as a group of soldiers gave chase.

"The house then collapsed because of a bomb," said army Captain Mohanned Ibrahim. "The gunmen escaped through a back door."

Major Hussam Karim at the provincial security command said the initial house bomb had killed six troops and wounded two others, while a second, delayed, bomb hidden in the garden killed two soldiers and injured two.

Dr Abdulrazzaq Mustafa at Saadiyah hospital confirmed the toll.

In Baghdad on Wednesday, meanwhile, the head of a maternity hospital was shot dead by gunmen who tied up her husband before killing her, an interior ministry official said.

He said Dr Intissar Hassan Mohammed, chief of the Al-Alwiya maternity hospital in central Baghdad, was shot dead but her husband was spared.

Two traffic police were also gunned down in the capital, while a rocket attack on the southern neighbourhood of Dora killed one person and wounded three others, the official added.

According to the Iraqi medical association, the country had 34,000 doctors in the 1990s, but that dropped to just 16,000 in 2008, in the aftermath of the chaos that followed the US-led invasion that ousted dictator Saddam Hussein during which time doctors and nurses were targeted.

The violence comes as Iraq observes Ramadan, which began on Wednesday for Sunnis and will start on Thursday for the country's majority Shiites.

In previous years the Muslim holy month of fasting has coincided with a spike in insurgent activity.

Iraq is also grappling with a five-month-long political impasse after a March 7 parliamentary election failed to produce a clear winner, ushering in as yet fruitless coalition negotiations between the leading parties.