Congress is debating whether to approve Obama's measure to take military action against Syrian President Bashar Assad's regime, which the U.S. administration holds responsible for an Aug. 21 chemical weapons attack that killed more than 1,400 people..
Should Congress not approve the measure, Cruz, in an appearance on ABC's "This Week," said Obama shouldn't be able to move forward with the strike.
"It would be contrary to the Constitution," he said.
Some republicans have suggested such an action by Obama would be an impeachable offense.
"I think a military attack is a mistake," Cruz said of Obama's proposed plan.
“One because I think the administration is proceeding with the wrong objective, and two, because they have no viable plan for success,” he added. “They are beginning from the wrong objective because this attack is not based on defending U.S. national security… I don’t think that’s the job of our military to be defending amorphous international norms.”