Story by the Associated Press/Curated by Liz Klimas

WASHINGTON (AP) — Two Republican foreign policy hawks said Monday that President Barack Obama needs to make a strong case for attacking Bashar Assad’s Syria if he wants to win congressional backing.

At the same time, Sens. John McCain of Arizona and Lindsey Graham of South Carolina said it would be a mistake for Congress to reject Obama’s request.

“We have to make it clear that a vote against this would be catastrophic in its consequences,” now and in future international crises, McCain told reporters outside the White House following a private meeting that he and Graham had with Obama.

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US Senator John McCain, R-AZ, answers a question as Senator Lindsey Graham, R-SC, looks on following their meeting with US President Barack Obama at the White House in Washington, DC, on September 2, 2013. McCain said Monday that Congress’s failure to authorize military action in Syria would be “catastrophic” because it would undermine US credibility. (Photo: JEWEL SAMAD/AFP/Getty Images)

Said Graham: “A degrading strike limited in scope could have a beneficial effect to the battlefield momentum. There will never be a political settlement in Syria as long as Assad is winning.”

McCain, who has been pressing Obama for over a year to intervene militarily in Syria as the civil war there has widened, said the administration’s plan now could be more difficult because Assad “is moving his forces around.” Both McCain and Graham questioned the wisdom of the administration publicly signaling in advance its intention to strike.

Watch some of McCain and Graham’s remarks:

Obama had said earlier this year that any documented use of chemical weapons by Assad against his own population would amount to a “red line” that the international community would not let him cross. Obama now has called for a military response to Assad’s purported use of chemical weapons, and the administration said Sunday it had evidence he used the chemical sarin gas in a Damascus suburb recently.

McCain and Graham, who often speak in unison on foreign policy matters, talked to reporters in the White House driveway after a lengthy meeting with the president.

McCain said he believes lawmakers awaiting a critical vote on Syria “must be assured that this is different from the past two years of neglect” on the part of the administration.

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US Senator John McCain holds his notes. (Photo: JEWEL SAMAD/AFP/Getty Images)

He also said he differs with the administration’s view that there was sufficient time to seek an authorization from Congress.

“I am not satisfied that the timeline is of no consequence and I am astounded when the chairman of the Joint Chiefs of Staff says it doesn’t matter,” McCain said, referring to Army Gen. Martin Dempsey.

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