Honolulu ? President Barack Obama on Monday vowed to use “every element of our national power” to keep Americans safe and said the failed Christmas Day plot to blow up a Detroit-bound airliner was “a serious reminder” of the need to continually adapt security measures against changing terrorist threats.

But even as Obama spoke, word came that a State Department warning had failed to trigger an effort to revoke the alleged attacker’s visa. And officials in Yemen confirmed that the would-be bomber had been living in that country, where terrorist elements quickly sought to take credit for his actions.

The incident prompted stiffer airport boarding measures, and authorities warned holiday travelers to expect extra delays as they return home this week and beyond.

Umar Farouk Abdulmutallab, 23, charged with trying to destroy an aircraft, is being held at the federal prison in Milan, Mich. A court hearing that had been scheduled for Monday to determine whether the government can get DNA from him was postponed until Jan. 8. No reason was given.

Calling Abdulmutallab’s action an “attempted act of terrorism” Obama vowed to “do everything that we can to keep America safe” and declared: “The United States will more than simply strengthen our defenses. We will continue to use every element of our national power to disrupt, to dismantle and defeat the violent extremists who threaten us.”

Members of Congress, meanwhile, questioned how a man flagged as a possible terrorist managed to board a commercial flight into the United States carrying powerful explosives and nearly bring down the jetliner. Sen. Joe Lieberman, I-Conn., said Monday that the Senate Homeland Security and Governmental Affairs Committee that he chairs would hold hearings in January.

Meanwhile, al-Qaida in the Arabian Peninsula claimed responsibility for the thwarted attack as retaliation for a U.S. operation against the group in Yemen. Yemeni forces, helped by U.S. intelligence, carried out two airstrikes against al-Qaida operatives this month in the lawless country that is fast becoming a key front in the war on terror. The second one was a day before Abdulmutallab attempted to bring down a Northwest Airlines flight as it prepared to land in Detroit.