Contradicting President Obama's assertion, Republican Sen. Ted Cruz of Texas said this morning on "This Week" that the president does not have the authority to order a military strike on Syria without Congressional approval.

"I don't think he has the authority," Cruz told ABC's George Stephanopoulos.

"It would be contrary to the Constitution," he added later, when Stephanopoulos asked him if acting without Congressional approval would be an impeachable offense, as some republicans have suggested.

President Obama said last month that while he was in favor of a military strike on Syria and believed he could order one without Congressional authorization, he would seek the approval of Congress before he ordered military strikes against the Middle Eastern nation for its alleged use of chemical weapons last month that the United States says killed close to 1,500 people, including more than 400 children.

ABC News

The president will address the American people Tuesday night in a nationally televised addressed. The day before, he'll sit down for interviews with the country's five major networks and PBS.

An unofficial tally by ABC News suggest that a resolution to strike Syria would fail in the House of Representatives and a recent ABC News/Washington Post poll found that nearly 6 in 10 Americans opposed a unilateral U.S strike on Syria.

Cruz has been a critic of the President's push for military action against Syria, saying on "This Week" Sunday that "I think a military attack is a mistake."

"One because I think the administration is proceeding with the wrong objective, and two, because they have no viable plan for success," Cruz said. "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."

Earlier on "This Week," White House chief of staff Denis McDonough said he was "outraged" by Cruz's recent comments that the U.S. military would be serving as "Al Qaeda's air force" by undertaking air strikes.

Cruz told the website The Blaze last week that "We should be focused on defending the United States of America. That's why young men and women sign up to join the military, not to, as you know, serve as Al Qaeda's air force."

"I am outraged for somebody to suggest that our people would be serving as allies to Al Qaeda," McDonough said on "This Week" when asked about Cruz's comment.

Cruz defended the remark on "This Week," saying U.S. strikes could potentially aid rebel forces with links to Al Qaeda.

"Just because Assad is a murderous tyrant doesn't mean his opponents are any better… Either the strike is really significant, it weakens Assad and the result is the rebels are able to succeed, and if that happened there is Al Qaeda taking over, or Al Nusra taking over, and extremist terrorists getting access to those chemical weapons, that hurts U.S. national security," Cruz said.

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