WASHINGTON — The Army could begin drawing down its troop levels in Iraq as soon as next year in what would be the first significant drop in U.S. forces since the beginning of the war, according to one of the Army's top generals.

Gen. Richard Cody, the Army's vice chief of staff, said yesterday that he sees the next rotation of troops in Iraq as being smaller than the current standing force of about 138,000 troops, though he declined to speculate on how much smaller. He said top combat commanders are discussing the possibility of a smaller U.S. presence in Iraq over the next two years, a decision that could come as soon as April, when Gen. George Casey, who commands the troops in Iraq, meets with defense officials in Washington.

Another defense official, who asked not to be identified, told Reuters yesterday that the number of U.S. Marines in Iraq also was likely to decline in the new rotation.

For there to be any drawdown, Iraq security forces must continue to improve their ability to fight the insurgency themselves, Cody said.

The military is planning a staggered rotation of soldiers and large units that will be in Iraq between 2006 and early 2008, Cody said.

The military has not selected which units will serve in Iraq during that rotation. They would replace the Army's 4th Infantry and 101st Airborne divisions, which are slated to go to Iraq in the coming rotation.

The insurgency has forced the United States to keep the 138,000 troops, or 17 brigades, in Iraq since the U.S.-led invasion two years ago. They are primarily Army soldiers and Marines, members of units that stay in Iraq for a year at a time.

About 150,000 U.S. troops are in Iraq now because 12,000 extra were sent for security during the Jan. 30 elections. The additional forces are scheduled to leave within two weeks.

Another 22,700 allied, non-Iraqi troops are also in the country, a number that has been dropping as more countries have pulled out forces. Italian Prime Minister Silvio Berlusconi indicated this week that Italy may begin reducing its 3,000-strong contingent this year amid anger over the recent, accidental killing of an Italian intelligence officer by U.S. troops.

The Pentagon says any reductions in foreign allied troops will be made up by Iraqi security forces, which have meanwhile grown to more than 140,000 soldiers and police who have received training and equipment. The quality and capabilities of these forces vary widely, and it is unclear whether all the police are actually on the job.

If the situation in Iraq worsens, it is possible that the U.S. force level would remain steady or even grow, officials say.

Initial U.S. postwar planning for Iraq anticipated the United States would be out of Iraq by the end of 2004, according to Army documents. After the invasion, the U.S. set its goal at the end of 2005.

Now there's no end in sight, and Bush administration officials have become cautions about suggesting any precise timeframe for a withdrawal. On Wednesday, President Bush declined to set a timetable for bringing American forces home and said he hoped allied forces would also stay the course.

In violence around Iraq, six U.S. soldiers were wounded in the northern city of Mosul when a convoy was attacked by a car bomber, Capt. Patricia Brewer said in Baghdad. According to a witness, Faisal Qasim, the attack was done by a suicide bomber who slammed his car into a convoy of seven armored vehicles, striking the fourth.

Also yesterday, outgoing U.S. Ambassador John Negroponte returned to the United States after a near nine-month stint. Negroponte has been named U.S. director of national intelligence.

Charge d'affaires James Jeffrey will take over the Baghdad post temporarily. Administration officials say President Bush will likely replace Negroponte with Zalmay Khalilzad, an Afghan-American serving as the ambassador to Afghanistan.