The United States says it will suspend some $800 million in military aid to Pakistan.

White House Chief of Staff William Daley told ABC's This Week that the U.S. relationship with Pakistan is difficult and must be made to work over time. He says that until the two nations get through those difficulties, the U.S. will hold back some of the money that American taxpayers have committed to give.

Earlier Sunday, The New York Times cited three unnamed senior U.S. officials who said the move is aimed at chastening Pakistan for expelling American military trainers and to press Pakistan's army to fight militants “more effectively.”

The newspaper reports the aid curtailment is “clearly intended” to force the Pakistani military to choose between backing the country that finances much of its operations, or continuing to provide “secret support” for the Taliban and other militants fighting American soldiers in Afghanistan.

Ties between Washington and Islamabad have been frayed since the surprise U.S. raid that killed al-Qaida leader Osama bin Laden in Pakistan in early May.