WASHINGTON: Three senior US senators warned Afghan President Hamid Karzai on Thursday that not signing a Bilateral Security Agreement would pose a threat both to Afghanistan and the surrounding region.

Senators John McCain, Lindsey Graham and John Barrasso met President Karzai earlier in the day to inform him that the US Congress too wanted him to sign the agreement for enabling some American troops to stay in Afghanistan after 2014.

The United States plans to withdraw most of its troops from Afghanistan by December 2014 but intends to leave behind a small, rapid deployment force for fighting militants and training Afghan security forces.

While President Karzai acknowledges the need for continued US troop presence in Afghanistan, he refuses to sign the proposed dealing, saying that a new president elected in April should do it. The proposed deal is also a congressional requirement for allowing the US administration to deploy troops in Afghanistan after 2014.

In statements issued by their offices in Washington, the three senators said they had urged President Karzai to resolve his disagreements with the United States over the deal as soon as possible.

Senator McCain said he was confident that the deal would be signed despite the delay because “the differences have been narrowed to the point that we can resolve them soon”.

The senators said they had also discussed with President Karzai an Afghan plan to release hundreds of “dangerous prisoners” from Bagram prison, handed over from US to Afghan control in March.

Senator Graham said he told Mr Karzai “if these releases go ahead it will do irreparable damage to the relationship”.

Washington considers 88 of some 650 prisoners marked for release a serious threat to security, because they were responsible for wounding or killing 57 Afghans and 60 US and coalition troops.

The Pentagon announced on the New Year eve that by Dec 31, 2013, at least 2,162 US troops had been killed in Afghanistan. At least 134 more died in support of Operation Enduring Freedom.

While summing up US war efforts in Afghanistan, a Pentagon official said that despite the losses the United States was willing to keep some troops in the country after 2014.

“We are prepared to sign the agreement,” said acting Pentagon spokesman Steven Warred.“We urge the government of Afghanistan to sign the agreement promptly. If we cannot conclude a BSA promptly, we will be forced to initiate planning for a post-2014 future that does not have a US troop presence there.”