(Reuters) - U.S. Defense Secretary Robert Gates made an unannounced trip to Pakistan on Thursday, hoping to deepen ties and persuade the nuclear-armed U.S. ally to root out all militants on its soil, including Afghan Taliban factions.
Here are some questions and answers about U.S.-Pakistani relations:
Pakistani support is crucial for the United States as it strives to defeat al Qaeda and bring stability to Afghanistan. Pakistan has captured and handed over to the United States numerous al Qaeda members, including Sept. 11 plotter Khalid Sheikh Mohammed. Osama bin Laden is believed to be hiding somewhere along the lawless Afghan border.
The army is attacking Pakistani Taliban militants, but the United States is pressing Islamabad to act also against Afghan Taliban factions, based in northwestern Pakistani border enclaves, it blames for surging violence in Afghanistan.
The U.S. military says Afghan Taliban leaders are based in Pakistan "reportedly" aided by elements of Pakistan's main spy agency. Pakistan denies that, as well as a U.S. assertion that an Afghan Taliban leadership council is based in the Pakistani city of Quetta.
A large volume of supplies for the U.S. military in landlocked Afghanistan is trucked from Pakistan's Karachi port.
The United States is Pakistan's biggest aid donor and has given about $15 billion in direct aid and military reimbursements since 2002, about two-thirds of it security related. While Pakistan is being propped up by an $11.3 billion International Monetary Fund loan, a new U.S. aid package triples non-military assistance to Pakistan to $1.5 billion a year over the next five years. Conditions attached to the package -- including those related to counter-terrorism and nuclear non-proliferation efforts -- angered many Pakistanis, including the powerful military. Pakistan would also like the United States to press India to resolve the core dispute between the nuclear-armed South Asian rivals, the divided region of Kashmir. India is opposed to outside involvement.
There is suspicion on both sides and analysts speak of a "trust deficit". Many Pakistanis feel the United States has blown hot and cold toward them based on its own strategic interests. The United States used Pakistan as a staging area to help supply Afghan fighters who drove the Soviet Union from Afghanistan in 1989. It subsequently largely retreated from the area, leaving Afghanistan in chaos and many Pakistanis and Afghans feeling abandoned. Many Pakistanis are opposed to U.S. involvement and polls show a majority of Pakistanis hold an unfavourable view of the U.S. government.
Pakistan, which has lost about 2,000 soldiers fighting the Taliban, is angered by repeated U.S. calls for it to do more.
The United States has expressed confidence in the safety of Pakistan's nuclear weapons but it remains worried about nuclear proliferation.
Strikes by missile-firing U.S. drones on militants in northwest Pakistan have also enraged many Pakistanis, although some U.S. officials say the strikes are carried out under an agreement that allows Pakistani leaders to decry the attacks in public. Pakistan denies that and warns that any expansion of strikes, or incursions by U.S. ground troops, would damage ties.
U.S. officials said last month Pakistan was delaying hundreds of visas for U.S. officials and contractors which could hamper U.S. aid programmes and further strain their alliance. Most recently, Pakistan has been angered that its citizens will be subjected to special checks when flying to the United States under new U.S. regulations introduced after a Nigerian tried to blow up a U.S. airliner on Christmas Day.
Editing by Alex Richardson