Calls for Congress to authorize even limited military action in Iraq heated up Wednesday as a leading Democrat on the Senate Foreign Relations Committee demanded that lawmakers have a say before the United States uses force in Iraq.

In a biting Washington Post op-ed followed by a lengthy floor speech on June 25, Sen. Tim Kaine, D-Va., argued that President Barack Obama "must" come to Congress before launching airstrikes or taking other military action.

The strong message from the chairman of the Foreign Relations subcommittee on Near Eastern and South and Central Asian affairs suggests support for unilateral executive action may be fraying as Baghdad itself no longer appears in imminent danger of falling as it did last week.

"I do not believe that this president — or any president — has the ability, without congressional approval, to initiate military action in Iraq or anywhere else, except in the case of an emergency posing an imminent threat to the US or its citizens," Kaine said on the Senate floor. "And I also assert that the current crisis in Iraq, while serious and posing the possibility of a long-term threat to the United States, is not the kind of conflict where the president can or should act unilaterally. If the United States is to contemplate military action in Iraq, the president must seek congressional authorization."