(CNN) -- President Barack Obama's counterterrorism adviser, John Brennan, met the president of Yemen to discuss al Qaeda and U.S. support for Yemen, the U.S. Embassy there announced Monday.
Brennan delivered a letter to Yemeni President Ali Abdullah Saleh affirming U.S. support for Yemen, the embassy said.
Al Qaeda activity in Yemen grabbed the attention of the West with the Christmas Day attempted bombing of a Northwest Airlines trans-Atlantic flight as it approached Detroit, Michigan.
The suspect, Umar Farouk AbdulMutallab, who has pleaded not guilty to six federal terrorism charges, was reportedly trained and armed in Yemen.
The Obama administration is considering adding armed CIA drones to help fight the increasing threat of al Qaeda in Yemen, a U.S. official said last month.
A counterterrorism official told CNN that the administration recognizes that "not enough is being done in Yemen" to meet the growing challenge posed by al Qaeda in the Arabian Peninsula.
"We need to scale up efforts to disrupt the group," added the official, who spoke about sensitive issues on the condition of anonymity.
According to the official, all options to fight the Arabian Peninsula group are under review at the White House.
Conditions in Yemen have allowed al Qaeda to regroup there, said the official.
"They've shown already that they can attack in Yemen and in the United States," the official said.
"They're not feeling the same kind of heat -- not yet, anyway -- as their friends in the tribal areas," the official said, referring to Pakistan. "Everyone involved on our side understands that needs to change."
The Washington Post reported August 25 that CIA analysts concluded that al Qaeda's offshoot in Yemen had become a more urgent threat to the United States than the core group in Pakistan.
The CIA would not comment on the Post report, but spokesman George Little told CNN: "This agency and our government as a whole work against al Qaeda and its violent allies, wherever they appear."
Al Qaeda in Pakistan remains a lethal enemy, said the counterterrorism official who spoke with CNN, and there would be no easing on that front or in the pursuit of terror chief Osama bin Laden and the rest of al Qaeda's leadership.
But with the help of allies, the United States has been able to score "lots of successes" against al Qaeda in Pakistan, the official said.
That includes the success of U.S. unmanned predator strikes in Pakistani regions along the border with Afghanistan.
Since the Obama administration took office at the beginning of 2009, missile attacks on suspected terrorists in Pakistan have increased dramatically.
The United States has "cut into their ability to plot, plan and train, but they remain very dangerous and they are still the hub to all spokes, the heart of al Qaeda," the U.S. official said.
"No one's even close to saying it's over in Pakistan. Not at all. In fact, we not only have to keep up the pressure there, we have to spread it to al Qaeda's nodes and affiliates elsewhere."
However, another U.S. counterterrorism official said the situation in Pakistan is very different from Yemen and it is unlikely the use of armed drones would happen soon in Yemen. This official said it took time for the United States to build up its relationship with the Pakistani government and to get the expertise in the tribal areas to carry out the missile strikes.
"The infrastructure cannot be built up overnight," said the official, who added, "It's not the weapon itself, but the information that guides the weapon that has to be there."
The Yemeni government has been fighting the growing al Qaeda in the Arabian Peninsula with the help of the U.S. military and intelligence assets.
The counterterrorism official said the larger role for the CIA will not limit the military's efforts. "There is enough work to go around," said the official.
Defense Department officials said both agencies remain involved in the Yemen campaign but added that the intelligence community can operate differently, a reference to the fact the U.S. military cannot take action without the approval of the host government.
Since its inception in January 2009, al Qaeda in the Arabian Peninsula has claimed responsibility for numerous terrorist attacks against Saudi, Korean, Yemeni and U.S. targets.
CNN's Pam Benson and Barbara Starr contributed to this report.