Kabul, Dec 7 (IANS): US Secretary of Defence Chuck Hagel Saturday arrived here for an unannounced visit, but won't meet Afghan President Hamid Karzai, an Afghan source said.

"The US secretary of defence arrived in Kabul Saturday evening and he will meet with the US and North Atlantic Treaty Organisation (NATO) commanders as well as with the US soldiers stationed in the country," the official told Xinhua.

The source said the Pentagon chief will not meet with Afghan president as his visit is aimed at meeting the troops at the end of year ahead of Christmas.

Relations between the two countries have remained strained over the signing of the Bilateral Security Agreement.

A four-day traditional Loya Jirga or grand assembly of the elders which ended Nov 24 has endorsed the agreement, but Karzai has said that the pact would not be signed until the presidential election on Apr 5, 2014.

Karzai attached some conditions to the signing of the accord, such as an assurance from the US that it will bring security to Afghanistan, ensure arranging a transparent election, and support the peace process with the Taliban.

The US wanted Kabul to sign the agreement by the end of 2013, warning that not signing it, would affect support by the US and its allied forces to militancy-plagued Afghanistan.

More than 86,000-strong NATO-led foreign troops are currently being deployed in Afghanistan.

Experts said if the two countries fail to reach the deal which governs the presence of the US troops after the 2014 pullout of the NATO-led forces, the US will consider complete withdrawal of troops, similar to the pullout of its troops from Iraq two years ago.