The Senate Foreign Relations Committee has passed a resolution condemning the president's plan for more troops in Iraq.
The vote on the Democratic resolution, which says the troop buildup "is not in the national interest," was 12-to-nine.
Nebraska Senator Chuck Hagel was the only Republican to support the nonbinding resolution.
He says the administration "better be damn sure" it knows what it's doing before sending more troops into what he calls "that grinder."
Committee chairman Senator Joseph Biden stressed it is an effort to prevent the president from making "a significant mistake" in Iraq.
But Tennessee senator Bob Corker said it will have "zero effect" on the administration.
Several Republicans who voted against the legislation expressed unease with the administration's new policy.
The measure is expected to come before the full senate next week.