U.S. will keep pressure on extremists: Obama

U.S. President Barack Obama says the government will use "every element" of its power to prevent attacks on U.S. soil in the wake of an in-flight bombing attempt on a Northwest Airlines flight.

"We do not yet have all the answers about this latest attempt, but those who would slaughter innocent men, women and children must know that the United States will do more than simply strengthen our defences, " Obama said from Hawaii where he has been vacationing with his family.

Obama said he has directed his national security team to keep up the pressure against America's enemies and that the U.S. will not rest until all who were involved in the attempted plane attack are held accountable.

"We will continue to use every element of our national power to disrupt, to dismantle, and defeat the violent extremists who threaten us, whether they are from Afghanistan or Pakistan, Yemen or Somalia or anywhere where they are plotting attacks against the U.S. homeland," Obama said.

Umar Farouk Abdulmutallab, 23,  is accused of trying to light an explosive device on Northwest Airlines Flight 253 from Amsterdam on Friday.

Obama has also ordered an examination of the overall watch list system in place — which is used to identify known and suspected terrorists — and how it can be strengthened.

"We need to determine just how the suspect was able to bring dangerous explosives aboard an aircraft and what additional steps we can take to thwart future attacks," Obama said.

The U.S. government has said that Abdulmutallab had been on a broad watch list that includes more than 500,000 names after his father alerted embassy officials in Nigeria in November about his son's religious beliefs.

But U.S. Homeland Security Secretary Janet Napolitano has said there was not enough information to put him on a no-fly list, which contains the names of people deemed to be a threat to the security of aircraft or air travellers.

Obama said he has also ordered a review of airport screening procedures.

Once he was first notified of the incident, Obama said he took steps to make sure all flights still in the air were secure and could land safely.

He said officials have enhanced screening and security procedures for all domestic and international flights and added federal air marshals to flights entering and leaving the U.S.