US Defense Secretary Robert Gates urged Pakistan on Friday to put pressure on all militant groups based in its lawless northwest, not just Al-Qaeda-linked Pakistani Taliban attacking the state, but Afghan Taliban too. Here are some questions and answers about the groups and the US and Pakistani positions: Which groups is Pakistan fighting? The military is fighting Pakistani Taliban factions behind bomb and other attacks in Pakistan, most against the security forces and other government targets. Their attacks intensified sharply after the military used force to clear out a radical mosque complex in the capital, Islamabad, in July 2007. The army launched an offensive against Pakistani Taliban in the Swat valley, northwest of Islamabad, last April and largely cleared them out after three months of clashes. In October, it began an offensive against the main Pakistan Taliban bastion in South Waziristan, on the Afghan border. Troops have captured most of their bases and most militants have fled. Security forces have also been fighting a third main Pakistani faction in the Bajaur region at the northeastern end of the ethnic Pashtun tribal belt on the Afghan border. Militants based there began attacking security forces after US drone aircraft began attacking their Al-Qaeda allies in the region. The army has also been attacking smaller groups of Pakistani Taliban fighters in other parts of the northwest such as the Khyber, Kurram and Orakzai regions. Who are the other groups? Other groups focus on fighting Western forces in Afghanistan. A main Afghan Taliban faction in South Waziristan is led by a commander known as Maulvi Nazir. Nazir's men have at times battled Pakistani Taliban fighters in South Waziristan, most of whom come from a rival ethnic Pashtun tribe. In North Waziristan, there is an Afghan Taliban faction led by commander Gul Bahadur. While relations between the government and those groups are at times tense, and clashes have occured, both groups have had peace pacts with the military. A more powerful group in North Waziristan, allied with Bahadur, is led by veteran Afghan guerrilla commander Jalaluddin Haqqani. The so-called Haqqani network, now increasingly led by his son, Sirajuddin, for years had close links with Pakistani security agencies. It also has links with Al-Qaeda. It, too, like the other Afghan Taliban factions, does not launch attacks inside Pakistan but sends its men across the border to fight Western forces there. US and Afghan officials say another main Afghan Taliban faction based in Pakistan is the Quetta Shura, run by a leadership council headed by reclusive Afghan Taliban chief Mullah Mohammad Omar. US commanders say the faction is run from the city of Quetta in Pakistan's southwestern Baluchistan province. Its fighter infiltrate into southern Afghanistan from a Pashtun-dominated region on the border. Pakistan denies that the Quetta Shura exists. How about the former anti-Soviet fighters? Another faction fighting in Afghanistan with links in Pakistan is the Hezb-i-Islami, run by Gulbuddin Hekmatyar. He, too, was a veteran guerrilla commander during the Soviet war. Hekmatyar was then the Afghan faction leader closest to Pakistan. His whereabouts are not known and while most of his men are believed to be inside eastern Afghanistan his group has support among Afghan refugees in Pakistan. What is Pakistan's position? Pakistan is fighting the groups that pose the greatest danger to it, the ones attacking security forces and setting off bombs in its cities. Pakistan has a tradition of using Islamist fighters for foreign policy aims and analysts say it is nervous about the growing influence of old rival India in Afghanistan, and about the prospect of US forces pulling out and leaving the country in chaos. For these reasons, analysts say, Pakistan is reluctant to begin hostilities with groups that pose no danger to it and which could provide leverage in Afghanistan, and a safe bet for pursuing a long-term goal of a friendly Kabul government, especially if attempts gather pace to bring elements of Afghan factions into some kind of peace deal. What does the us want? The United States, while praising action against the Pakistani Taliban, is also pressing Islamabad to go after the Afghan factions. Announcing his strategy for the Afghan war in December, US President Barack Obama said the United States would not tolerate militant havens in Pakistan. Gates said making a distinction between Pakistani Taliban and their Afghan allies was counterproductive and he called for Pakistan to pressure Afghan factions. But Gates, keen to build trust with the Pakistani military, did not repeat the usual US call to “do more.” He said it was up to Pakistan to decide when to act.