Obama also renewed his call to for tightening gun control measures.
The FBI has identified Syed Rizwan Farook, 28, a Pakistani-American, and his wife Tashfeen Malik, 27, a Pakistani national -- as having carried out the deadly massacre in San Bernardino.
The couple were killed by police in an exchange of fire on Wednesday after they were chased down following their assault in which 14 people were killed.
This is for the first time that the US President has conceded that the deadliest shooting in recent years may have been a result of radicalisation, a fear long dreaded by US law enforcement agencies after the 2008 Mumbai terror attack in which a radicalised American national played a key role.
"We know that ISIL and other terrorist groups are actively encouraging people around the world and in our country to commit terrible acts of violence, often times as lone wolf actors," said the US President.
"And even as we work to prevent attacks, all of us -- government, law enforcement, communities, faith leaders -- need to work together to prevent people from falling victim to these hateful ideologies," he said.
Referring to the ongoing investigations by the FBI, Obama, who did not name the couple, said they are learning more about the killers.
This tragedy reminds of the obligation to do everything in power, together, to keep communities safe, Obama said.
"This is work that should unite us all as Americans, so that we're doing everything in our power to defend our country. That's how we can honour the lives we lost in San Bernardino," he said.
