President Barack Obama on Monday laid out immediate steps that he is taking to ensure public safety following a foiled Christmas Day effort to blow up a Northwest plane bound for Detroit from overseas.In his first public remarks since the aborted attack, Obama said he has ordered an immediate review of the nation’s watch-list system and air safety regulations. Actions taking effect immediately include adding federal air marshals to flights entering and leaving the United States and reviewing screening measures at airports.Obama reinforced that his national security team will keep up the pressure on those who may try to attack. People who want to harm Americans “must know the United States will do more than simply strengthen our defenses,— Obama said. Speaking from a Marine base in Hawaii, where he has been on vacation, the president called on Americans to be vigilant, but also confident in their country’s ability to thwart terrorist attacks.The administration has come under fire from Republican critics who say it has not taken the threat of terrorist attacks seriously. Homeland Security Secretary Janet Napolitano conceded Monday on NBC that the aviation security system “did not work in this instance.— Her comments were a reversal from comments that she gave Sunday on CNN, when she said the system worked “once the incident occurred.— She later said she was referring to the system of notifying other flights and law enforcement about the incident after it happened.