Image caption Adm Mullen said it would be dangerous to abandon Islamabad

The top US military officer has acknowledged "very significant" cuts to US military numbers in Pakistan, saying US-Pakistan ties need time to heal.

Adm Mike Mullen, head of the Joint Chiefs of Staff, said some of the US troops, mostly trainers, would remain.

Pakistan asked the US to reduce its troop presence after US special forces killed Osama Bin Laden last month.

The raid sparked deep anger in Pakistan, further damaging already strained ties with the US.

The US has provided Pakistan with billions of dollars of aid in recent years, much of it military assistance.

Washington sees its relations with Pakistan as vital in the fight against al-Qaeda and against Taliban militants in Afghanistan who use safe havens in Pakistan's tribal regions on the border.

But with al-Qaeda leader Bin Laden now known to have been living undetected almost next door to a major Pakistani military academy, many in the US Congress have questioned the value of the US aid.

'Introspection'

Before Bin Laden was killed on 2 May in a raid on his compound in northern Pakistan, the US had about 200 troops in Pakistan. Most of them were helping to train the Pakistani army.

"There clearly is an ongoing contraction of that support... and it is tied to the difficult time we are going through," Adm Mullen told reporters in Washington after a visit to Pakistan.

Image caption There have been protests across Pakistan over the US raid to kill Osama Bin Laden

Adm Mullen said the raid to kill Bin Laden had triggered "a great deal of introspection" in Pakistan.

"They're going to have to finish that before we get back to a point where we are doing any kind of significant training with them," he said.

For now, he said, that meant "a very significant cutback in trainers".

"I think we need to give them a little time and space to do that [introspection]," he said. "And that makes all the sense in the world to me."

But he said it would be dangerous to abandon Islamabad.

"I think the worst thing we could do would be cut them off," he said. If that happened, he said, "10 years from now, 20 years from now, we go back and it's much more intense and it's much more dangerous".

Adm Mullen steps down as chairman of the Joint Chiefs of Staff later this year.