WASHINGTON, Dec. 5 — Robert M. Gates, President Bush’s nominee to be defense secretary, won unanimous approval today from a Senate panel after testifying that the United States was not winning in Iraq and that American failure there could ignite “a regional conflagration” in the Middle East.

At one point, Mr. Gates said it was “too soon to tell” whether the American invasion in 2003 had been a good idea. He added: “My greatest worry if we mishandle the next year or two and leave Iraq in chaos is that a variety of regional powers will become involved in Iraq, and we will have a regional conflict on our hands.” Mr. Gates is expected to win confirmation from the full Senate as early as Wednesday to succeed Donald H. Rumsfeld. At the daylong hearing of the Senate Armed Services committee, Democrats and Republicans praised what they called Mr. Gates’s refreshing candor.

Mr. Gates gave few firm signals today about his own favored options for Iraq, but portrayed himself as a flexible realist, open to all options for adjusting American strategy. But he made clear that he has concerns about a rapid American drawdown, and cautioned that the recommendations to be made public on Wednesday by the Iraq Study Group would be important but not “the last word.”

"It’s my impression that frankly there are no new ideas on Iraq,” Mr. Gates said, noting there are multiple government reviews underway besides the Iraq Study Group. “The question is: is there a way to put pieces of those different proposals together in a way that provides a way forward?”