Former US Secretary of State Henry Kissinger said it would be a "catastrophe" if Congress did not back military action and "undermine the American position in the world" after Mr Obama made the use of chemical weapons a "red line" issue.
He told BBC Radio 4's Today programme action should be more than a "shot across the bows" but not go as far as intervening to influence the result of the civil war.
Obama made a personal appeal to the international community to unite in military action against 'barbarism' in Syria.
President Obama has received the support of prominent Republicans as he tries to gain backing for military action in Syria.
President Obama and his team are engaged in frenzied lobbying as lawmakers prepare to vote on a possible military strike in Syria.