BAGHDAD - Iraq's chief spokesman acknowledged differences with the United States over a proposed long-term security agreement and pledged yesterday that the government will protect Iraqi sovereignty in ongoing talks with the Americans.

Australia became the latest member of the U.S.-led coalition to pull combat soldiers from Iraq, fulfilling an election promise that helped sweep Prime Minister Kevin Rudd to power in November.

Meanwhile, an American soldier was killed yesterday by an armor-piercing roadside bomb in northeastern Baghdad, the military said. No further details were released.

And two U.S. soldiers were injured when their helicopter crashed yesterday south of Baghdad, the military said. The military said the crash was being investigated but appeared to be due to mechanical failure.

Opposition has been growing in Iraq to the proposed security pact with the U.S., which will replace the current U.N. mandate and could provide for a long-term American military role in this country.

Much of the opposition comes from anti-American Shiite cleric Muqtada al-Sadr, but statements critical of the deal have also been issued by mainstream Sunni and Shiite figures who fear it will undermine Iraqi sovereignty.

Chief government spokesman Ali al-Dabbagh said the Iraqi negotiators have a "vision and a draft that is different" from the Americans but that the talks, which began in March, were still in an early stage.

U.S. officials have refused to comment on the talks until they are complete but have insisted they are not seeking permanent bases. The agreement is to replace a U.N. mandate for U.S.-led forces that expires at the end of the year.

At the same time, the U.S. command is facing a dwindling coalition of allied countries that provide combat power in Iraq.

Rudd, the new prime minister, has said the Iraq mission had made Australia more of a target for terrorism and had promised to bring home his country's 550 combat soldiers by the middle of this year. *