**US Defence Secretary Robert Gates is in Pakistan for talks with military and civilian leaders.**Mr Gates is making his first visit to Pakistan, a key US ally, since President Obama took office last year.
The trip comes at a crucial time in the fight against al-Qaeda and the Taliban, with the US planning to send tens of thousands more troops to Afghanistan.
Talks are expected to focus on how to combat militants in Pakistan’s tribal areas bordering Afghanistan.
Correspondents say the United States would like to see Pakistan expand an offensive against Taliban in the area.
Mr Gates is also expected to raise concerns that Pakistan is delaying the extension of visas of US officials.
The BBC’s Syed Shoaib Hasan in Islamabad says the main issue on Pakistan’s agenda is likely to be the increased use of drone strikes by the US in Pakistan tribal areas.
Hundreds of people have died in the attacks, which have stoked deep resentment of the US among many Pakistanis.
‘Syndicate’
The US defence secretary flew into Islamabad on Thursday from talks in Delhi.
Arriving in the Pakistani capital, Mr Gates said he would reassure his hosts that the United States is “in this for the long haul”.
Pakistan has been an important US ally in the fight against militants in South Asia since the 11 September 2001 attacks in the US.
On Wednesday, Mr Gates said al-Qaeda was trying to destabilise the whole of South Asia hoping to provoke war between India and Pakistan.
In comments which might unsettle some in Pakistan, Mr Gates suggested India might not show restraint if it suffered another attack like the one in 2008 on Mumbai.
Blamed on Pakistan-based militants, the attack killed more than 160 people.
Peace talks between the two countries, who have fought three wars since independence from Britain, have been on hold ever since.
Mr gates said militant groups in South Asia - the Taliban in Afghanistan and in Pakistan, and the Pakistan-based group Lashkar-e-Taiba - were seeking to spark conflict between India and Pakistan, or to provoke instability in Pakistan.
“It is not unreasonable to assume that Indian patience would be limited were there another attack”
Robert Gates,
US defence secretary
US diplomats in Pakistan visa row
He said: “It’s dangerous to single out any one of these groups and say, ‘If we can beat that group, that will solve the problem,’ because they are in effect a syndicate of terrorist operators intended to destabilise this entire region.”
When one group succeeded in carrying out an attack, all of them gained in capability and reputation, he said.
“A victory for one is a victory for all.”
Correspondents say the US would like to see India and Pakistan working together against the militant threat - but Mr Gates said co-operation would be a tough sell.
Mr Gates said any conflict between India and Pakistan would only further the militants’ agenda - as well as throwing American policy in Afghanistan and Pakistan into disarray.
‘Suspicions’
The defence secretary also praised the “extraordinary” financial aid India had given Afghanistan, but acknowledged this had created tension with Pakistan.
“There are real suspicions both in India and Pakistan about what the other is doing in Afghanistan,” he said.
“So I think each country focusing its efforts on development, on humanitarian assistance, perhaps in some limited areas of training, but with full transparency for each other, would help allay these suspicions and frankly create opportunities.”
Reports in recent days have suggested the US would like India to help train Afghan police.