Pakistan has reopened its routes for pullout of Nato troops from Afghanistan after the US extended an apology for the killing of 24 Pakistani soldiers in November.

Islamabad had said the move would cement the fractured relationship between the two countries. The Pakistan decision will also help the US save hundreds of millions of dollars.

As soon as the announcement of the supply routes surfaced, the Pakistan Taliban declared it would attack the troops.

"We will attack Nato supplies all over Pakistan. We will not allow anyone to use Pakistani soil to transport supplies that will be used against the Afghan people," Reuters quoted a Taliban spokesperson as saying from an undisclosed location.

Earlier, US Secretary of State Hilary Clinton in a statement recalled US regret over the November deaths. "I once again reiterated our deepest regrets for the tragic incident in Salala last November. I offered our sincere condolences to the families of the Pakistani soldiers who lost their lives. Foreign Minister Khar and I acknowledged the mistakes that resulted in the loss of Pakistani military lives.

We are sorry for the losses suffered by the Pakistani military. We are committed to working closely with Pakistan and Afghanistan to prevent this from ever happening again," said Clinton.

The relationship between the two countries hit a new low after the killing of the Pakistani soldiers and Islamabad closed its supply routes to Afghanistan which are crucial for Nato troops' withdrawal in 2014.

The transit fees for the troops are also likely to remain the same against Islamabad's earlier threat to increase it. Islamabad threatened to demand around $5,000 per truck against the previous fixed rate of $250.

Reports suggest that the Obama administration also promised to provide other benefits such as road construction and improved domestic infrastructure to seal the deal, although there is no official confirmation.

Islamabad had often expressed its embarrassment about the use of US drones as part of US strategy against militants.