Faced with an increasingly alarming threat from al-Qaida in the Arabian Peninsula, the U.S. military will begin a new training program with Yemen's counterterrorism unit so it can move against militants believed to be plotting attacks on America from safe havens there.

The effort will mark the first time the U.S. has trained the counterterrorism unit, which has traditionally focused on protecting Yemen's capital, according to a senior defense official. Under the plan, the training would begin in the next few months, and the Yemenis could more than double the size of their counterterror force, which now numbers about 300.

The official spoke on condition of anonymity because details are still being worked out.

The plans come as the U.S. watched rippling public unrest rattle many of its Middle Eastern allies, including autocratic leaders such as Egypt's former President Hosni Mubarak, who stepped down Friday.

On Sunday Yemeni police used truncheons to stop protesters, many of them university students, from reaching the capital's central Hada Square. Witnesses said plainclothes policemen wielding daggers and sticks also joined security forces in driving the protesters back.

Yemen's president Ali Abdullah Saleh also postponed a trip to Washington scheduled for next month due to the "circumstances in the country," the state news agency reported.

Mubarak and Saleh both worked with the U.S. to counter terrorism, and cooperation with Yemen is considered critical by U.S. national security leaders to combat AQAP.

So far, U.S. defense officials said there has been no impact on U.S.-Yemen military cooperation as a result of the public protests, and that Yemen remains committed to its operations against AQAP. As an example, Yemen has created what one official called a "hard mission force" within the counterterror unit that they want trained to do more precise strikes.

The new training program would expand U.S. military assistance to Yemen, where AQAP has planned and launched several attack against the U.S., including the attempted airliner bombing on Christmas Day 2009 and the failed mail bomb plot involving cargo planes last summer.

Senior U.S. intelligence officials told Congress Thursday that AQAP is committed to obtaining weapons of mass destruction, including chemical and biological agents. And the group is still focused on inspiring homegrown American militants to launch their own attacks from within the U.S.

"The likelihood of obtaining a biological weapon is more likely than obtaining or producing a yield-producing nuclear device," National Counterterrorism Center director Michael Leiter said during a hearing Thursday. "I do think that the smaller-scale lone wolf attack with conventional weapons still stands out as the far more likely event."

U.S. officials have repeatedly warned that AQAP is the most significant and immediate threat to America, largely through smaller-scale attacks. Leaders of the insurgent group post persistent threats online saying they intend to continue to plot and execute attacks, and urge others to do the same.

Anwar al-Awlaki, the American-born radical cleric who is believed to be the inspiration for the Christmas Day attack and a growing participant in assault planning, is reportedly hiding in Yemen.

The new training program in Yemen will cost about $75 million, the defense official said. And the goal is to create a national counterterror unit that will be better able and equipped to travel out to tribal regions and ferret out insurgents hiding there.

To date the U.S. military, with about 100 trainers rotating in and out of Yemen, has been working with that country's special operations forces and their military, particularly aviation units.

The new program would become part of that overall training effort, but officials believe it will provide a critical step toward getting at militants in safe havens, particularly in the Abyan and Shabwah provinces.

Future spending totals are in flux as Congress has not yet approved the 2011 defense budget.

Military transport has been a persistent challenge for the Yemenis, but just in the last month, the U.S. delivered four Huey helicopters to Yemen and has been training the aviation units. The aircraft will help the Yemeni forces get troops, equipment and supplies to combat outposts in the more remote tribal regions.

The helicopters also will eventually allow Yemen to do more operations that involve precise strikes with a small number of troops, the defense official said.

The official said that the U.S. is assessing now how it can best help Yemen battle AQAP. The counterterror unit expansion is a key element of that, along with deciding how many military outposts are needed in the tribal regions, and how big the counterterror force should be.

The overall U.S. effort also includes economic and governance assistance.

Officials also say that while AQAP is one of the most active al-Qaida franchises, there has been little insurgent travel between Yemen and Pakistan, where Osama bin Laden and his top lieutenants are believed to be hiding.

Persistent assaults by the U.S. and Pakistan — including an escalating campaign of drone strikes into the Pakistani border region — have put pressure on core al-Qaida, making it more difficult for them to travel or communicate with others.