Secretary of State John Kerry, who days ago made an impassioned case for a military strike against Syria, on Sunday defended President Obama’s surprise decision to delay a strike, saying the next move is up to Congress.

Kerry, appearing on Fox News Sunday, rejected the argument that delaying the use of force weakens the nation’s hand in stopping Syria’s use of chemical weapons.

President Obama on Saturday announced that rather than ordering the military strikes against Syria that most everyone expected, he would instead delay making a decision until Congress votes on the matter when it returns in nine days from a summer recess.

“Haven’t you handed Syria and Iran at least a temporary victory?” host Chris Wallace asked Kerry, who is making the Sunday talk show rounds.

“I don’t believe so at all, and that is in the hands of the Congress of the United States,” Kerry said. “The president has made his decision. The president wants to stand up and make certain we uphold the international norm and do not grant impunity for a ruthless dictator to gas his own people.”

Kerry added, “America’s credibility is on the line here and I expect the members of the congress of the United States to do what is right, to stand up and be counted.”

But the approval of Congress is far from certain, even according to lawmakers who will vote in favor of authorizing the president to launch a military strike.

In addition to a large faction of anti-war Democrats, the Congress includes a growing number of Republicans, many with Tea Party roots, who are far less supportive of U.S. military intervention in foreign countries than their more mainstream GOP colleagues.

“It is going to be difficult to get the vote through Congress,” said Rep. Peter King, R-N.Y., a top lawmaker on the House Homeland Security Committee.

King said if the House were to vote today, the measure would likely fail, in part because the president appears to have wavered in his own commitment to the strike by making the surprise decision to delay action.

“When they see the president so weak and vacillating, many will vote no,” King said.

The Senate and House announced plans to consider the authorization measure the week of Sept. 9.

The Senate Foreign Relations Committee and Armed Services Committee will both meet this week to consider the matter.

Several high-ranking Democrats have announced support for the measure, including Senate Foreign Affairs Committee Chairman Bob Menendez, of New Jersey, and Senate Majority Leader Harry Reid, D-Nev.

King and other lawmakers called on Obama to request that Congress reconvene immediately so as to shorten the delay of any military strike.

Kerry, however, made the case Sunday that postponing action until later in September would not handicap the initiative.

“The case doesn’t change at all,” Kerry said on Fox. “The rational…is as powerful today and will be as powerful if not more powerful with each day.”

Kerry said that hair and blood samples from the first responders to the chemical attack in Syria show evidence that deadly sarin gas was used.

But other lawmakers said Obama’s indecision on Syria will weaken the power of the United States to stop the global proliferation of weapons of mass destruction.

“This is a clear failure of leadership,” King said. “If [Obama] doesn’t want to take the action himself, then he should call us back into session tomorrow. If we can’t stop Syria on a red line with chemical weapons, then how can anyone expect us to stop Iran with a red line, with respect to nuclear weapons?”

On ABC’s This Week, George Stephanopoulos asked Kerry what would happen if Congress voted down the resolution, Kerry said he wasn’t even contemplating that outcome.

“I don’t contemplate that—I think the stakes are just too high here,” he said, later adding: “George, we are not going to lose this vote. The president of the United States is committed to securing the unity of the purpose that he believes strengthens America. And I believe the Congress will see that that’s the responsible thing to be done here.”