The U.S. government has added dozens of people to the ominous lists of suspected terrorists and those barred from U.S.-bound flights, a crackdown that comes as President Barack Obama is poised to announce changes to the nation's watchlists.

At the White House on Tuesday, Mr Obama will speak in fresh detail about the findings of the urgent, sprawling reviews he ordered of how the government screens airline passengers and how it works to detect and track possible terrorists. Mr Obama's remarks, to come after his meeting with top security and intelligence officials, will outline steps designed to strengthen the watchlisting effort and to thwart future terrorists attacks, the White House said.

The move comes after what officials call a botched effort by a Nigerian man to blow up an airliner over Detroit on Christmas, one that exposed cracks in the U.S. security system, which is built upon the ability of agencies to share information and connect dots.

Meanwhile, people flying to the U.S. from overseas will continue to see enhanced security. The Transportation Security Administration has directed airlines to give full-body pat-downs to U.S.-bound

travellers from Yemen, Nigeria, Saudi Arabia and 11 other countries the U.S. believes have terrorism activity _ a move criticised by one Muslim advocacy group.

The addition of more names to the government's terrorist watch and no-fly lists came after U.S. officials closely scrutinised a larger database of suspected terrorists, an intelligence official said Monday. People on the watch list get additional checking before they are allowed to enter this country; those on the no-fly list are barred from boarding aircraft in or headed for the United States.

A 23-year-old Nigerian man who claimed ties to al-Qaida was charged Dec. 26 with trying to destroy a Detroit-bound airliner as it approached the airport. Umar Farouk Abdulmutallab is alleged to

have sneaked an explosive device onto the plane and then set it off, sparking a fire but not the intended mass explosion.

Abdulmutallab's name was in the government's database of about 550,000 people suspected of having terrorism ties. But it wasn't on a list requiring him to pass through additional security screening

or keep him from flying to the U.S. That prompted a review of the National Counterterrorism Center's

massive Terrorist Identities Datamart Environment database and spurred the enhanced security screening protocol issued Monday.

An intelligence official discussed the changes in the watch list on condition of anonymity because the official was not authorised to speak publicly. The official said that after the Dec. 25 incident, counterterrorism officials reviewed information in TIDE on people from countries where terrorists have operated.

The security breach competed for the president's attention as he juggled other matters _ his final push to get health care legislation through Congress, the ever-present drive to ease the nation's employment woes, and an approaching State of the Union policy address to spell out his second-year agenda.

Mr Obama's meeting Tuesday will be his most comprehensive, hands-on briefing since the failed terrorist attack rocked the nation. Those Mr Obama has tapped to conduct the reviews include agency heads at the

highest levels _ all of them central figures across the intelligence and homeland security landscape.

Mr Obama will get updates on the investigation from FBI Director Robert Mueller, on the prosecution of the suspected terrorist from Attorney General Eric Holder, and on the review of terrorist detection techniques from Homeland Security Secretary Janet Napolitano.

Counterterrorism adviser John Brennan will update Mr Obama on his review of the terror-watch system and offer findings, and agency heads will comment on their own internal assessments.

Mr Obama prepped for the big meeting on Monday, meeting privately with security aides.

``With respect to what happened with the terrorist on the plane coming into Detroit, we are not satisfied,'' Secretary of State Hillary Rodham Clinton told reporters Monday. ``The president has

called for a whole-of-government review.''

Abdulmutallab told U.S. investigators he received training and instructions from al-Qaida operatives in Yemen. Law enforcement officials said Abdulmutallab ignited an explosive mixture, but it failed to seriously damage the plane. The explosive device, which some say may have been designed to evade U.S. security restrictions, was hidden below the Nigerian's waist.

As a result, people who are from, travelling from or through these countries are supposed to have full-body pat-downs or scanning, go through explosive detection technology, and have their carry-on luggage inspected: Cuba, Iran, Sudan, Syria, Afghanistan, Algeria, Iraq, Lebanon, Libya, Nigeria, Pakistan, Saudi Arabia, Somalia and Yemen.

The U.S. has designated Cuba, Iran, Sudan and Syria as state sponsors of terrorism. The other 10 countries are considered ``of interest,'' based on the latest intelligence.

The Council of American-Islamic Relations, known as CAIR, said that these measures amount to religious profiling because so many people from these countries are Muslim.

``Under these new guidelines, almost every American Muslim who travels to see family or friends or goes on pilgrimage to Mecca will automatically be singled out for special security checks _ that's profiling,'' said Nihad Awad, CAIR's national executive director. The TSA said it does not profile.

``TSA security measures are based on threat, not ethnic or religious background,'' TSA spokeswoman Kristin Lee said. The new security measures were to go into effect Monday, but several European countries were still scrambling to digest and implement the new rules.

Mr Obama returned to Washington Monday from an 11-day Hawaii vacation that was dominated by news of the Dec. 25 incident. He received regular updates about the security scare and spoke twice to the nation, sandwiching those events around beach time, golf and relaxation with his family.

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