FACTBOX: Is Pakistan's Taliban war about to get bigger?

ISLAMABAD (Reuters) - Militants ambushed a Pakistani military convoy in North Waziristan on the Afghan border this week killing 16 soldiers and threatening to open a new front for the army in its campaign against the Taliban.

The militants were from a faction led by a commander, Gul Bahadur, who agreed to a peace pact with the government last year. A faction spokesman said his men would now go on the offensive against the army.

There are numerous militant factions in Pakistan's northwest with differing objectives, some intent on forcing foreign troops out of Afghanistan, others fighting Pakistan.

WHICH GROUPS IS PAKISTAN FIGHTING?

The military launched a drive two months ago in the Swat valley, northwest of Islamabad but not on the Afghan border, against a Taliban faction led by a commander known as Fazlullah. The government has also ordered an offensive against Pakistani Taliban leader Baitullah Mehsud in South Waziristan, on the Afghan border. Both factions have been fighting Pakistani security forces and carrying out bomb attacks. Last year, the army went on the attack against close Mehsud ally, Faqir Mohammad, in the Bajaur region at the northeastern end of the ethnic Pashtun tribal belt on the Afghan border. The area had become an al Qaeda hub and Mohammad's men had also attacked Pakistani security forces. Some al Qaeda-linked factions of groups nurtured in the 1990s to battle Indian forces in the disputed Kashmir region have also "gone rogue" and are attacking the Pakistani state.

WHO ARE THE OTHER GROUPS?

Other groups have traditionally focused on fighting Western forces in Afghanistan. Another main faction in South Waziristan is led by a commander known as Maulvi Nazir. In North Waziristan, there is Bahadur's group and a network led by veteran Afghan guerrilla commander Jalaluddin Haqqani, whose men fight Western forces in Afghanistan. The Afghan Taliban also operate out of enclaves on the Pakistani side of the border, with many leaders believed to be based in Baluchistan province. Like the Haqqani network, the Afghan Taliban do not launch attacks in Pakistan.

PAKISTAN'S POSITION

Some analysts say Pakistan is fighting the groups that pose the greatest danger to it, the ones attacking security forces and setting off bombs in cities, while largely ignoring the groups that fight in Afghanistan. Pakistan has a tradition of using Islamist fighters to achieve foreign policy aims and analysts say it is nervous about the growing influence of old rival India in Afghanistan, and about the prospect of U.S. forces pulling out and leaving the country in chaos. For these reasons, analysts say, Pakistan is reluctant to open hostilities with groups, such as the Haqqani network and Afghan Taliban, which pose no danger to it and which could provide leverage in Afghanistan.

WHAT NEXT?

The attack by Bahadur's men and his scrapping of the peace deal raises the prospect of an expanding insurgency. But the military will be reluctant to open a new front in North Waziristan while it still faces pockets of resistance in Swat and is preparing to go after Mehsud in South Waziristan. However, a military spokesman said this week unspecified action would be taken in response to the Sunday ambush. Analysts expect a limited response, perhaps involving air strikes. The military might also seek help from the Haqqani network, Bahadur's allies, to rein him in and keep a lid on North Waziristan while if focuses on South Waziristan.

(Editing by Jerry Norton)