WASHINGTON: Delaying the signing of a US-Afghan security pact poses more of a psychological than logistical problem because it jeopardises Afghan troop “confidence,” the US military's top officer said Wednesday.

US and Nato officials have been pressing Kabul to sign the agreement without further delay or else risk a complete withdrawal of Western troops after 2014 and drastically reduced international aid.

The United States likely has until the “early summer” before a delay would start to constrict possible military “options” in Afghanistan, said General Martin Dempsey, chairman of the US Joint Chiefs of Staff.“So that's not the limiting factor,” he told reporters when asked about the accord.

But he said dozens of countries contributing troops to the Nato-led mission needed the pact signed to be able to make plans and that Afghan security forces would be “anxious” with the future presence of Western troops in question.

“Don't forget that we're not in this alone,” Dempsey said.

“We've got 44, I think, troop-contributing nations who have a different set of requirements to make their decisions, and so... we will see an erosion of the coalition,” the four-star general said.

“And by the way, the other thing we'll see is an erosion of confidence by the Afghan security forces... as they begin to be anxious, literally, about whether we're going to be there to support them.”

Afghan President Hamid Karzai so far has declined to sign the Bilateral Security Agreement, or BSA, which would lay out the legal conditions for US and allied forces to stay in Afghanistan after 2014 on a mission mainly focused on training.

US officials have urged Afghanistan to approve the accord, which was endorsed by a so-called “loya jirga” gathering of thousands of Afghan tribal elders, by the end of the year.

“So it really needs to be done now, mostly because what's hanging in the balance in Afghanistan is confidence,” Dempsey said.

“The Afghan Security Forces are very capable, but they're not confident.”

There are now 46,000 American troops and 27,000 forces from other coalition countries on the ground in Afghanistan, while Afghan security forces have reached about 345,000.

The bulk of the Nato-led forces are due to pull out by the end of next year.

Under the post-2014 mission, up to 12,000 troops — mostly American — would be stationed in the country.

Dempsey said he had not yet been asked to start planning for a scenario in which all US troops would be withdrawn after 2014.

“I have not been told to plan for a zero option, but clearly, I understand that it is a possibility given the current impasse,” he said.