Seldom visible in the Yemeni mountains, the elite U.S. commandos training the Yemen's military represent the Obama administration's quest to fight terrorism without inflaming anti-American sentiment.
That balancing act has become an administration trademark, funneling millions of dollars in aid and low-profile military trainers to countries such as Pakistan and Yemen in order to take on a more diverse, independent and scattered al Qaeda network.
The scope and amount of the military training in Yemen has grown slowly, reflecting the Pentagon's intention to tackle the terrorism threat while still being sensitive to fears that a larger U.S. footprint in Yemen could help fuel the insurgency.
Over the past year, the number of elite U.S. trainers moving in and out of Yemen has doubled, from 25 to about 50. The numbers fluctuate depending on the training schedule, but U.S. forces now are providing a more complex level of instruction that combines tactical ground and air operations.
At stake is the stability of a troubled, poverty-stricken nation struggling to thwart al Qaeda-linked terrorists who are growing stronger and increasingly are targeting the U.S. and other Western interests.
"Yemen is the model for how we're going to conduct counterterrorism in the future," said Rick Nelson, a counterterrorism analyst at the Center for Strategic and International Studies. "It is not going to be large-scale intervention, as it was under the Bush administration, and not because it is or isn't working, but because it's economically unfeasible" to wage expensive wars.
The U.S. has placed unprecedented priority on Yemen, State Department counterterrorism coordinator Daniel Benjamin said last week, describing a two-pronged program to root out terrorists while targeting the "incubators for extremism" — such as poverty, weak governance and corruption.
Speaking at the U.S. Institute of Peace, Mr. Benjamin said the U.S. is on track to provide as much as $300 million in military, humanitarian and development this year. About half of that is for military equipment and training.
He said the president has ruled out active U.S. military intervention in Yemen and instead wants to focus on building that government's capacity to deal with its own social and security problems.
The terrorism threat from Yemen has escalated in the past 18 months, with estimates that about 300 al Qaeda members or cells are operating there. The gravity of the situation deepened after the failed Christmas Day attack of an airliner over Detroit was linked to al Qaeda in the Arabian Peninsula, which is based in Yemen.
Yemen is also the base of U.S.-born radical cleric Anwar al-Awlaki, who is thought to have helped inspire the airline plot and other attacks in the U.S. The administration has the fugitive Mr. al-Awlaki on a kill-or-capture list.
The U.S. military training in Yemen, said one senior defense official, is aimed at fixing shortfalls in the Yemeni military's aviation, intelligence and tactical operations. There also is training for the maintenance of aircraft and other systems.
Several U.S. and Yemeni officials spoke on the condition of anonymity to describe the U.S. training effort, which is rarely discussed in public because of its politically sensitive nature.
In general, the U.S. trainers never appear in public. The U.S. special operations forces are thought to be concentrated in a mountainous area in western San'a, the capital. Yemeni counterterrorism troops and British special operations trainers are participating with the U.S. trainers.
Yemeni authorities have been careful not to discuss the U.S. presence. Yemeni President Ali Abdullah Saleh said during a Ramadan sermon last month that Yemen does not accept the presence of foreign troops in its territory. However, he acknowledged in March that American trainers are in Yemen.
"There is no American presence on Yemen's land and seas," he said. "There is U.S.-Yemeni cooperation in counterterrorism, in training. And mission numbers no more than 40 to 50 people."
Mr. Saleh is concerned about his delicate alliance with the hard-line groups and tribes that are most threatened by U.S. operations. Yemeni media have accused the weak central government of giving up its sovereignty by allowing foreign troops to use Yemen as a battlefield against al Qaeda.
The careful growth of training by U.S. troops in Yemen mirrors a slow expansion of a Pentagon counterterrorism training program in Pakistan, which officials say serves as a workable road map for building U.S. military relationships with government forces in terrorist strongholds.
The U.S. instruction of Pakistan's paramilitary Frontier Corps, while enhancing the capabilities of the nation's security forces, also makes it easier for American commanders to gather intelligence, establish contact with local populations and move more freely in the country.
U.S. trainers in Pakistan operate mainly in two training centers along the Afghan border. But their proximity to terrorist strongholds can also be a drawback. Earlier this year, three of the trainers were killed and two others wounded by a roadside bomb.
Analysts on the Gulf region warn that military aid must be supplemented with economic, development and governance support.
Too much emphasis on defense programs could make Yemen more militaristic, fuel militant recruiting and provide resources for the government's internal struggles against Shiite Hawthi rebels in the north and a secessionist threat in the south, said Christopher Boucek, a Yemen analyst at the Washington-based Carnegie Endowment for International Peace.
"If we just focus on the military and security for them to become more lethal, it's not going to improve the country's security; it will only fuel recruitment and grievances," Mr. Boucek said.
Mr. Boucek, who was in Yemen earlier this year, said the increased military training force is more visible there now. During that growth, the country has transformed from being a place for terrorists to hide out or train to a place where militants can participate in jihad.
"More people are going there, they are more lethal and dangerous, and there is room for it to grow," he said.
U.S. training efforts in Yemen are part of a multi-pronged counterterrorism campaign that over the past year has included surveillance and intelligence sharing, along with several targeted cruise missile strikes directed at al Qaeda leaders.
More than 40 people were killed in December by air raids targeting al Qaeda leaders. Yemenis have reported sightings of unmanned aircraft hovering over the provinces of Shabwa and Marib, known as hide-outs for al Qaeda militants.
U.S. officials have said recently that they are looking at using armed Predator drones to hunt down and kill al Qaeda leaders operating out of safe havens in Yemen's ungoverned regions. But such operations would be conducted only with the acceptance of Yemeni leaders, officials said.
The Pentagon has pledged $150 million in military assistance to Yemen this year for helicopters, planes and other equipment.
A senior Yemeni official said the government is looking most for a sense of commitment from the United States that does not ebb and flow as terrorist incidents with a Yemen tie occur.
In January, the country's most influential Islamic cleric, Sheik Abdel-Majid al-Zindani, warned against "foreign occupation." Sheik al-Zindani is an extremist who once associated with Osama bin Laden and whom the U.S. has called "a specially designated global terrorist."
Senior U.S. military and counterterrorism officials say al Qaeda leaders in Pakistan — including bin Laden — present the most serious threat and could best plan and execute a complex Sept. 11-style attack against the United States.
The U.S. now has a more formal, established program there. To date, special operations forces have trained about 1,500 members of the Frontier Corps and 2,000 members of the Pakistani military.