| KAILUA, Hawaii
KAILUA, Hawaii A wing of al Qaeda claimed responsibility on Monday for a failed Christmas Day attack on a U.S.-bound passenger plane and President Barack Obama vowed to bring "every element" of U.S. power against those who threaten Americans' safety.
In a statement posted on Islamist websites, the group Al Qaeda in the Arabian Peninsula said the attempt was to avenge U.S. attacks on its members in Yemen.
The group said it had provided the Nigerian suspect in the failed airliner bombing with a "technically advanced device" but that it did not detonate because of a technical fault.
Umar Farouk Abdulmutallab, 23, is charged with smuggling explosives on board and attempting to blow up a Northwest Airlines flight as it approached Detroit from Amsterdam on December 25 with almost 300 people on board.
Speaking during a vacation in Hawaii, Obama said, "We will not rest until we find all who were involved and hold them 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."
Abdulmutallab, who had a valid U.S. visa issued before he was placed on a broad U.S. list of possible security threats, has told investigators that al Qaeda operatives in Yemen gave him an explosive device and taught him how to detonate it, officials said over the weekend.
The incident has put a spotlight on the growing prominence of al Qaeda in Yemen, which the United States and Saudi Arabia fear will exploit instability in Yemen to stage attacks in the Saudi kingdom, the world's largest oil exporter, and beyond.
The United States has quietly been supplying military equipment, intelligence and training to Yemeni forces, who have raided suspected al Qaeda hide-outs this month, U.S. defense and counterterrorism officials said.
In a worrying development for U.S. security, officials have discovered that Abdulmutallab's father warned them of his son's growing radicalism, but this information failed to prevent his traveling to the United States on a two-year visa issued June 16, 2008.
Obama said that as a result of this oversight, he had ordered a thorough review of the screening process.
"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.
Obama is under pressure from opposition Republicans who have been critical of his response to the Christmas Day scare and have questioned whether his administration is doing enough to contain security threats.
His administration admitted on Monday that the incident represented a failure of air security.
Asked on NBC's "Today" show if the security system "failed miserably," U.S. Homeland Security Secretary Janet Napolitano replied, "It did."
On Sunday, Napolitano said the system to protect air travel worked, but in appearances on news shows on Monday she said she had meant that the response to alert other flights and airports and impose immediate new safety procedures had been effective.
Abdulmutallab was overpowered by passengers and crew on the Northwest Airlines flight 253 after setting alight an explosive device attached to his body. He was treated for burns and is in federal prison awaiting trial.
Airline stocks fell on Monday as the United States tightened airline security after the incident. AMR Corp, the parent of American Airlines, lost 4.8 percent to $7.75. Shares of Delta, the parent of Northwest, were down 4.1 percent to $11.29.
NEW SECURITY MEASURES
The U.S. Transportation Security Administration did not give details of its new security measures. But air travelers described new restrictions on flights headed for the United States, including additional preflight screening, and -- an hour before landing -- a ban on movement around the cabin and on having items such as blankets on passengers' laps.
The agency has since given pilots and flight crews discretion to ease these in-flight restrictions, a source familiar with the TSA rules said on Monday.
A TSA spokeswoman declined to confirm the change, saying the agency "will continuously review and update these measures to ensure the highest levels of security."
Senate Homeland Security chairman Joe Lieberman, an independent who usually votes with Democrats, said he plans a January hearing to investigate the incident, including why Abdulmutallab was not checked against what the senator said was "our broadest list of suspected terrorists" and why body-imaging scanners are not used on more passengers.
Dutch airport authorities said they planned to make new, more sensitive passenger scanners mandatory after Abdulmutallab allegedly smuggled explosives in his underwear through Schiphol Airport security.
(Additional reporting by Firouz Sedarat in Dubai, Debbie Charles, Adam Entous and Patricia Zengerle in Washington and Bernie Woodall in Detroit; Chuck Mikolajczak in New York and Camillus Eboh in Abuja; Writing by Jackie Frank, editing by Frances Kerry and Doina Chiacu)