Tanks and armored vehicles formerly belonging to the Libyan Army sit in a lot in Zintan, in the Nafusa Mountains, Libya. (ED GILES/For The Washington Post)

Deepening divisions among Libya’s myriad armed groups are increasingly stirring conflict in the North African state. Now the United States and its allies are prepared to add a new force to the toxic mix.

U.S. officials say the hope is that theGeneral Purpose Force — a trained Libyan military organization — will start to fill the country’s festering security vacuum, initially by protecting vital government installations and the individuals struggling to make this country run. The Obama administration hopes the force eventually will form the core of a new national army.

The first steps are small. At the request of Prime Minister Ali Zeidan, the United States, Britain and Italy have agreed to train 5,000 to 8,000 troops, many of whom will be drawn from existing militias. The recruits will be taken outside of Libya for military instruction and what a senior U.S. defense official described as an attempt to “shift attitudes and create new allegiances” to the central government.

But it remains unclear whether more men in arms can make a difference in an atmosphere flush with hundreds of powerful armed groups — many of them already on the government payroll — and competing political agendas.

Some in Libya, along with a number of outside experts, worry that the new force — whose recruits will be selected by the Libyan defense minister and vetted by the country that trains them — could ultimately become a tool for competing groups to advance their agendas, or simply one more armed faction in a dangerous sea of firepower.

Two years after dictator Moammar Gaddafi’s bloody demise at the hands of rebels, Libya’s sense of national unity is deteriorating rapidly. With powerful militias, tribes and parties vying for power, the increasing violence has included a number of deadly clashes and even a kidnapping of the prime minister, Zeidan.

The United States and its partners, who say they are training to “NATO standards,” are not the only ones moving to fill the security vacuum. A wealth of outside actors are rushing to bolster favored militias or to capi­tal­ize on the oil-rich country’s prevailing anarchy. Turkey is conducting military training for up to 3,000 Libyan recruits, and wealthy Persian Gulf states — as well as private companies and black-market arms dealers — are supplying favored groups. Morocco, Algeria and Tunisia also have expressed willingness to play a role in training Libya’s security forces, U.S. officials said.

“We have certainly seen multiple agendas playing out in the course of multiple external partners,’’ said the U.S. defense official, who spoke on the condition of anonymity to describe the touchy situation and U.S. goals.

For now, Libya’s government and legislature are weak and divided along a deepening fault line. On one side is a liberal-leaning coalition known as the National Forces Alliance, supported by heavily armed militias from the western mountain town of Zintan. On the other side are Islamist groups that include the Muslim Brotherhood and Islamist militias.

The more secular alliance supports Zeidan, along with Libya’s Defense Ministry, and controls Tripoli’s international airport and other major installations. Its Islamist rivals are more closely affiliated with the Interior Ministry.

Neither side wants the other to dominate a Libyan security force of the future.

“Any attempt to set up a new institution is seen as a zero-sum game — that this is a win by my rival,” said Frederic Wehrey, a Libya expert at the Carnegie Endowment for International Peace.

Even as the United States is shipping Humvees to the government, a Qatari businessman, who insisted that his name not be used, said he recently completed a $14.8 million deal that would supply 100 armored Toyota Land Cruisers to Islamist militias under the umbrella of Libya’s Interior Ministry.

Islamist militia leaders accuse the United Arab Emirates, Qatar’s gulf rival, of trying to counter Qatar’s influence by funneling money and training to more secular groups, particularly the Qaqaa brigade, a militia from Zintan that backs the National Forces Alliance.

When Libya’s deputy chief of intelligence, a man with ties to Islamists, was kidnapped last month from the Tripoli airport, his allies blamed the Qaqaa brigade.

Islamist militia leaders say they think that Western biases, prevailing anarchy and a lack of transparency mean that their more-secular foes ultimately have more to gain from the creation of a new force.

“Most of the guys who will get this training are from the Gaddafi regime,” said Moheidin al-Mejberi, an Islamist militia leader in Benghazi, referring to the more secular tribal alliance and the Zintan militias.

The United States is putting the finishing touches on a refurbished facility at Bulgaria’s Novo Selo training range, where it expects to receive an initial tranche of up to 350 Libyan recruits by spring. Plans call for a total of 4,000 troops eventually to be trained there, along with 2,000 each trained by Italy and Britain in those countries.

The Italians plan to pay for the training themselves; Libya will foot the bill for the Americans and British.

Lists of recruits are being compiled by the Libyan Defense Ministry, although “the pieces are still coming together” and no names have been provided to the United States, the U.S. defense official said.

The lists will be turned over to the U.S. Africa Command for vetting. Officials said they will use U.S. intelligence and other resources to exclude anyone with a connection to al-Qaeda.

U.S. officials said that Libyan groups such as Ansar al-Sharia, which U.S. intelligence has determined took part in last year’s attack on the U.S. diplomatic installation in Benghazi , should be easy to weed out.

Others — including an Islamist militia that the U.S. Embassy in Tripoli once employed for protection of the Benghazi mission, as well as powerful groups with hard-line Islamist ideologies such as Mejberi’s Supreme Revolutionary Operations Room and others that do much of the policing in the capital — may also fail to make the cut.

But “just because someone is in a militia doesn’t mean they can’t participate,” the U.S. defense official said. The official and others said that the United States was seeking vetted militia members and their commanders as fighters who can develop loyalties to the central government.

Once“removed from their environment . . . to reform and reorient them,” the defense official said, the recruits will spend the first half of their training on military skills and the second half learning to operate as a unit.

But according to militia leaders and activists in Libya, any large-scale exclusion of Islamists from the training program is more likely to spark a civil war than bring security.

“How effective are these ­forces going to be? Are the Islamists going to take to them lightly? No, of course not,” said Jalal al-Gallal, an activist and former member of the rebels’ Transitional National Council during the 2011 revolution.

The Bulgaria operation will not be the first U.S. training of Libyan security forces. In the summer, a handful of Special Forces troops set up a small training base outside Tripoli for a 100-strong elite Libyan unit. But the program was suspended two months ago after looters stole caches of weapons from the base in two overnight raids.

Some suspect an inside job among the trainees, but a senior U.S. official said the identities of the perpetrators are not known.

The trainees had been selected by Zeidan and vetted by the U.S. military, according to a U.S. official with knowledge of the program. It remains unclear who the trainees were and what their mission was — questions that have aroused suspicion among militia leaders and members of Libya's elected legislature.

U.S. defense and intelligence officials acknowledged the challenges of insulating any new force from old Libyan enmities. The plan, the defense official said, “is not without risk.”

But “in a context where institutions are close to nonexistent, and security is completely fragmented, how is it that you are able to change the tide?” the official said. “By starting with a small but still very ambitious focus on creating a force that is unified and has achieved a certain level of accomplishment.”

DeYoung reported from Washington.