Republican criticism

Hillary Clinton, the secretary of state, Robert Gates, the defence secretary, Leon Panetta, head of the CIA, Robert Mueller, director of the FBI, and Janet Napolitano, homeland security secretary, were among the administration heads due to meet the president on Tuesday to discuss the situation.

In depth

  Profile: The US counterterrorism bureaucracy
  Blogs: US air security shifts beyond borders

Obama, just back from an 11-day winter holiday in Hawaii, is facing scathing criticism from Republican politicians, who say he is weak on national security issues.

A White House spokesman insisted the renewed security concerns would not keep Obama from addressing rising unemployment in the country, and continuing to push for more healthcare reform.

"When you're president of the United States you've got to be able to walk and chew gum at the same time," Bill Burton, the spokesman, said on Monday.

But with two weeks to go before the one-year mark of his presidency, experts said Obama would be spending more time on national security issues than expected.

Airport screening

The administration on Monday imposed stricter screening regulations for US-bound airline passengers from Yemen, Nigeria and 12 other countries, including possible full-body pat-downs, searches of carry-on bags, and full-body scanning.

But the "enhanced screening" rules got off to a patchy start, amid complaints of delays and discrimination.

Several European governments, including Germany, France and Spain, said they were still studying the rules before implementing them.

With 13 of the 14 nations cited by the US Transportation Security Administration (TSA) being majority Muslim states, the Council on American-Islamic Relations (CAIR), a Muslim civil rights and advocacy organisation, said the procedures amounted to ethnic profiling.

"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," Nihad Awad, CAIR's national executive director, said in a statement.