A new report by the Congressional Budget Office is warning the U.S. military may have difficulties sustaining its current troop levels in Iraq beyond early next year. The finding is likely to fuel new debate over whether U.S. forces are being stretched too far by their overseas commitments.

The Congressional Budget Office says the military can only sustain a force of some 40,000 to 65,000 personnel in Iraq over the long term, a number far smaller than the current level of close to 130,000.

The report, released Wednesday, says a larger occupation force can only be maintained by extending the duty tours of soldiers, by deploying additional reserve units or by increasing the overall size of the Army.

It also says withdrawing soldiers from peacekeeping operations in Bosnia, Kosovo and the Sinai Peninsula along with pulling U.S. Marines from Okinawa could enable military planners to increase the size of the Iraq force.

The Pentagon had no direct response to the findings of the Congressional Budget Office report.

But in a statement, Defense spokesman Colonel Jay DeFrank says the Pentagon is continuously examining troop level requirements to ensure military commanders in Iraq have the forces they need.

The spokesman goes on to say that in this regard, defense officials will work closely with Congress and with the international community.

The Congressional Budget Office report does not get into the potential for U.S. allies to contribute to the Iraq mission.

There are now over 21,000 foreign troops in the country and the Bush administration is looking for new ways to attract greater international participation.

Until now, most of the foreign troops have been British. But a Polish-led international force took over security responsibilities in a part of central Iraq on Wednesday.

In addition to foreign troops, the Pentagon is working rapidly to increase the numbers of Iraqis involved in security operations in the country.