WASHINGTON: President Obama this morning directly linked the Christmas Day airline-bombing attempt to a Yemen-based branch of Al Qaeda, and he offered a full-throated defence of his administration's anti-terrorism efforts against Republican criticism.

In an Internet and radio address taped from his year-end vacation in Hawaii, Obama offered his most detailed public account yet of the ties between the global terrorist group and Umar Farouk Abdulmutallab, the Nigerian accused of attempting to detonate an explosive on Northwest Airlines Flight 253 from Amsterdam to Detroit.

Obama said in the address that it appeared Abdulmutallab joined an Al Qaeda affiliate in Yemen, which "trained him, equipped him with those explosives and directed him to attack that plane headed for America."

The president noted Al Qaeda's increased activity over recent years in Yemen, including bombings of American targets, and the US and Yemeni governments' efforts to strike back at the group.

"And all those involved in the attempted act of terrorism on Christmas must know: You too will be held to account," he said.

Obama also promised to hold accountable U.S. security officials -- including homeland security, law enforcement and intelligence officers -- in the wake of an ongoing review into breakdowns in terrorism screening that enabled Abdulmutallab to board the plane despite intelligence that suggested he could pose a threat.

The president reserved the longest stretch of the address to defend his terrorism policies and urge national unity in response to the attempted attack.

In an apparent direct response to former Vice President Dick Cheney, who last week accused Obama of "trying to pretend we are not at war" with terrorists, Obama said he had "made it very clear: Our nation is at war against a far-reaching network of violence and hatred, and that we will do whatever it takes to defeat them and defend our country."

The president stressed actions being undertaken in Pakistan, Afghanistan and Yemen and said, "Along with our partners, we've disrupted terrorist financing, cut off recruiting chains, inflicted major losses on Al Qaeda's leadership, thwarted plots here in the United States and saved countless American lives."

He took implicit shots at the Bush administration for its handling of wars in Iraq and Pakistan, noting that Iraq was not involved in the Al Qaeda-launched terrorist attacks of Sept 11, 2001.

At the same time, the president borrowed a page from the Bush playbook, urging lawmakers to overcome partisan divisions and "summon the unity that this moment demands." Senate Republican Leader Mitch McConnell issued a similar appeal for unity in the new year in a weekly address delivered today for the GOP.