While the Bush administration has downplayed prospects for permanent US bases in Iraq, General John Abizaid told a House of Representatives subcommittee on Tuesday he could not rule that out.
Abizaid said that policy would be worked out with a unified, national Iraqi government if and when that is established, "and it would be premature for me to predict".
Many Democrats have pressed President George Bush to firmly state that the United States does not intend to seek permanent military bases in Iraq, a step they said would help stem the violence there.
Abizaid also told the Appropriations subcommittee on military quality of life that while an Iraqi civil war was possible, "I think it's a long way from where we are now to civil war".
Echoing Bush's statement on Monday on the outlook for reducing US forces in Iraq, Abizaid said if Iraqis can form a unified government, "I think there's every reason to believe ... that we'll be able to bring the size of the force down much more so by December of '06".
Abizaid cited the need to fight al-Qaida and other extremists groups and "the need to be able to deter ambitions of an expansionistic Iran" as potential reasons to keep some level of troops in the region in the long term.
Abizaid called for a 'robust
But he said it would be far less than the 200,000 currently deployed in the region, including 132,000 in Iraq.
"Clearly our long-term vision for a military presence in the region requires a robust counter-terrorist capability," Abizaid said.
"No doubt there is a need for some presence in the region over time primarily to help people help themselves through this period of extremists versus moderates."
Abizaid also said the United States and its allies have a vital interest in the oil-rich region.
"Ultimately it comes down to the free flow of goods and resources on which the prosperity of our own nation and everybody else in the world depend," he said.
Representative David Price, a North Carolina Democrat, questioned "what kind of signal that sends to the American people and to the Iraqis and the region ... if somehow there is ambiguity on our ultimate designs in terms of a military presence in Iraq".
Last week the leading Democrat on the House Intelligence Committee, California Representative Jane Harman, wrote to President Bush urging him to clearly spell-out his plans in Iraq.
The administration's "continuing failure to clarify US intentions provides an excuse for certain Iraqis to avoid compromise and jeopardises our ability to succeed in Iraq," she said.