President Obama said the US is looking at limited action in Syria following a chemical weapons attack but the response would not be open-ended.
He said the attack threatened US national security and was a challenge to the world.
Canada is convinced that President Assad was behind the chemical weapons attack in Syria, Prime Minister Stephen Harper's chief spokesman said.
However, he reiterated that Canada had no plans for military action against Syria.
The UN Secretary General Ban Ki-moon returned to New York on Thursday evening and intends to engage with member states on developments in Syria, a spokesperson said.
His first meeting is due take place with the permanent members of the Security Council.
Former President George Bush told Fox News that Barack Obama had a "tough choice to make" over Syria but he was "not a fan of Mr Assad".
He said: "The President's got a tough choice to make and if he decides to use our military he will have the greatest military ever backing him up.
"I was not a fan of Mr Assad. He's an ally of Iran and he's made mischief."
Newspapers in America have said the Barack Obama is set for a solo strike on Syria after Britain rejected military intervention.
The Boston Globe goes with the headline, "In face of resistance, Obama is ready to act alone on Syria" while The Washington Post writes, "Obama can go it alone on Syria, British cooperation in any strike seems unlikely".
Turkish Foreign Minister Ahmet Davutoglu has said intelligence gathered by Ankara left no doubt that the forces of Syrian President Bashar al-Assad were responsible for a poison gas attack near Damascus last week.
"From our point of view, totally based on our national intelligence and assessments by our national experts...There is no doubt that the regime is responsible," Davutoglu told reporters.
The New York Daily News covered last night's vote in Parliament against military intervention in Syria with the headline: "The British aren't coming! The British aren't coming."
An NBC News poll found that 50 per cent of American people oppose military action in Syria. However, those numbers flip when the military action is defined to mean launching cruise missiles from naval warships – 50 per cent favour it, while 44 per cent oppose it.
And 58 per cent agree with the statement the use of chemical weapons by any country violates a “red line” that requires a significant US response, including the possibility of US action.
The survey also found eight in 10 Americans want President Obama to get congressional approval before using force.
Parliament's rejection of military action against Syria has been welcomed by Russia, AFP reports.