(Reuters) – Secretary of State Hillary Clinton arrived in Islamabad on Sunday, hoping to bolster shaky U.S. relations with a close ally in the struggle against militant insurgents in both Pakistan and neighboring Afghanistan.

Here are some facts about the importance and problem areas of the relationship, what aid has been given, what Pakistan wants and what is to come:

STRATEGIC IMPORTANCE

Pakistan is of huge strategic importance and a main ally for the United States as it seeks to defeat al Qaeda and cripple the Taliban in neighboring Afghanistan. Osama bin Laden, the mastermind of the September 2001 attacks on the United States, is believed to be hiding somewhere along the lawless border with Afghanistan. The leaders of the Taliban insurgency in Afghanistan are also believed to be hiding in Pakistan.

Washington is also pressing for Pakistan to step up the fight against its own homegrown Taliban militants, which U.S. officials believe were behind the attempted bombing in New York’s Times Square on May 1.

Washington needs Pakistan as it seeks to stabilize Afghanistan as U.S. President Barack Obama sends in an extra 30,000 troops in the coming months.

SECURITY COOPERATION

Much of Clinton’s meetings will focus on how to improve security cooperation, from intelligence-sharing to more equipment from the United States for its ally.

The two sides held an earlier round of talks in March and agreed to fast-track pending Pakistani requests for military equipment including helicopters, fighter jets and pilotless drones.

Washington has also pledged to deliver 1,000 laser-guided bomb kits to Pakistan and is considering more weapons sales to help Pakistan with insurgents in the Afghanistan border region.

KEY IRRITANTS

There is mistrust on a range of issues, from security cooperation to how aid is delivered. Most opinion polls show a majority of Pakistanis hold an unfavorable view of the U.S. government and are suspicious of its intentions. Pakistan’s government bristles when Washington complains it has not done enough to tackle militants in a war that has killed more than 2,000 soldiers and weighed on the economy.

Civilian deaths from drone strikes are also unpopular in Pakistan, although the civilian government is believed to privately support them.

A recent source of U.S. irritation has been delays in granting visas for U.S. officials wanting to audit how aid is spent while Pakistan complains about increased security checks for its citizens visiting the United States.

Clinton, in a visit to Pakistan in October, publicly expressed puzzlement that its government had been unable to find scores of al Qaeda leaders including Osama bin Laden who are believed to be hiding in rugged border territory that divides Pakistan and Afghanistan.

AID PROGRAMME

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.

The flow of money is being held up, however, as the Obama administration changes how it distributes that aid. Instead of largely using U.S. contractors and non-governmental organizations, it wants to funnel much of the aid via the Pakistani government and domestic NGOs in the hope this will bolster local capacity.

NUCLEAR COOPERATION

Pakistan would like a civilian nuclear cooperation deal with the United States, similar to the one Washington has with India, but there were scant signs of progress on this front during the March meetings.

The United States is leery of such a deal out of concern for how it might affect ties with New Delhi.

Pakistan President Asif Ali Zardari recently visited China amid signs that Chinese companies were ready to move ahead with plans to build two nuclear reactors for Pakistan, which could raise concerns in both Washington and New Delhi about nuclear proliferation.

(Editing by John O’Callaghan and Chris Allbritton)