KABUL: Doubts grew on Monday that the United States and Afghanistan could narrow sharp differences in negotiations and reach a long-term strategic partnership deal.

The Strategic Partnership Agreement, which Washington and Kabul have been discussing for over a year, will be the framework for US involvement in Afghanistan beyond 2014, when the last foreign combat troops are due to leave Afghanistan.

The Kabul government wants the United States and NATO to agree to stop carrying out night raids on Afghan homes as a precondition for signing an agreement with Washington and a timeline to assume control over detention centres.

But while the rules covering night raids and air strikes have been tightened, they continue to cause great resentment among many Afghans. Movement on the detention issue has also stalled, causing a deadlock.

"The impasse in talks could threaten the strategic partnership," said an Afghan foreign ministry official.

Relations have been heavily strained in recent weeks over the burning of copies of the Muslim holy book at a NATO base, which triggered violent protests and prompted some Afghan security forces to turn their weapons on American soldiers.

A senior Afghan government official told Reuters that Kabul has been pressing the Americans hard to hand over the detention facility at NATO's Bagram air base, where the Korans were burned.

"The United States government thinks Afghanistan does not have the ability or the international standards to run the prison and also insists that night raids can't be stopped overnight as it's a key tool against the insurgents," he said.

"The United States government believes that Afghan forces are not yet ready to take over the control of night raids from US troops," the official said.

Gavin Sundwall, a spokesman for the US embassy in Kabul, suggested a pact may not be possible. "We have always said it is more important to get the right agreement than to get an agreement," he said in a statement.

The Obama administration has been hoping it can conclude an agreement before a meeting of NATO leaders in Chicago in May.

While the document would not nail down details, it is expected to contain an agreement in principle to some sort of US military presence in Afghanistan beyond the end of 2014, when most NATO combat troops are expected to be gone.

A failure to broker a deal might strain US-Afghan relations, already complicated by the Koran burnings and a spate of insider attacks on foreign forces, even further. It would certainly raise questions about how the West can establish a stable future for Afghanistan as NATO nations bring their troops home.

In Washington, the State Department said the agreement remained an important goal.

"There have been a couple of sticking points. We are continuing to try to work through those and I don't have anything to report at this time with regard to completing the document or settling those two issues," State Department spokeswoman Victoria Nuland told reporters.

US officials have said the night raid and detention issues may be broken out into a separate document, perhaps allowing them to conclude the strategic partnership more quickly.

One US defense official said that "any round of negotiations on agreements of this significance is bound to surface disagreements from time to time. No one should suggest that we're at the point of failure."