WASHINTON - Fertilizer used in many IEDs targeting coalition troops comes from two factories in Pakistan. Pakistan warns decision will further worsen already bad ties between the two countries NATO air strike which killed Pakistan soldiers and secret raid which killed Osama bin Laden exacerbate frosty relationship U.S. has given $20bn in military and economic aid to Islamabad since Afghanistan war started in 2001

U.S. Congress has frozen $700million in aid to Pakistan until it gives assurances it is combating the spread of homemade explosives in the region.

Calls are growing in the U.S. to penalize Pakistan for failing to act against militant groups and, some argue, helping them.

Relations between the two countries are already at rock bottom after a number of U.S. drone attacks have killed Pakistani civilians and the secret raid in which al Qaeda leader Osama bin Laden was killed in May.

Pakistan is one of the largest recipients of U.S. foreign aid and the cutback announced is only a small proportion of the billions in civil and military assistance it gets every year.
Salim Saifullah, chairman of Pakistan's Senate foreign relations committee, warned ties could worsen further after the decision.