Pakistan's ISI chief heads to U.S. as ties flounder

ISLAMABAD (Reuters) - The head of Pakistan's powerful spy agency headed for Washington on Wednesday for unscheduled talks, the military said, days after the U.S. suspended a third of military aid over deepening tensions in their relationship.

Few details were immediately available about Lieutenant-General Ahmad Shuja Pasha's one-day trip, but it comes at a time when the Inter-Services Intelligence (ISI) is under intense pressure to sever ties with militant groups including those it has long nurtured as assets in Afghanistan and India.

Relations between the intelligence establishments of the two countries have been on a downward spiral since January after a CIA contractor killed two Pakistanis with joint operations against militants suspended soon after.

Then in May, the killing of Osama bin Laden in a secret raid by U.S. special forces further damaged the relationship, with Pakistan seeing the operation as a violation of its sovereignty.

Pasha was going to Washington to "coordinate intelligence matters," the military said in a one-line statement.

Incensed over the bin Laden raid, Pakistan drastically cut the number of U.S. military trainers allowed in the country and also set clear terms for U.S. intelligence activities in the country.

Washington, responded by saying it was holding back $800 million -- a third of $2 billion in security assistance -- in a show of displeasure over the cutback of military trainers, limits on visa for U.S. personnel and other bilateral irritants.

Despite protests by Pakistan in public, the United States has continued drone strikes in its northwest region, killing at least 48 suspected militants this week, one of the largest death tolls to date in the controversial air bombing campaign.,

(Editing by Chris Allbritton and Sanjeev Miglani)