Officials said intelligence reports and interviews with the Nigerian accused of trying to detonate explosives on a flight to Detroit, suggested other young men had been trained by al-Qaeda-linked groups.
Obama has reportedly ordered almost all the 3,200 existing air marshals, who are armed and work undercover, to be deployed to incoming flights by US airlines by Feb 1.
Agents from other law enforcement agencies would be called up to fill the gaps left on domestic flights that are deemed high risk.
"The rush is to get our people in place before they get theirs launched," a senior law enforcement official told ABC News. US government sources however said that no specific imminent threat had been detected.