WASHINGTON (Reuters) - The Taliban in Afghanistan have yet to decide to join renewed peace efforts despite an urgent need to get talks going before the spring fighting season begins in April, a senior U.S. administration official said on Thursday.

Delegates from Afghanistan, Pakistan, China and the United States held talks in Pakistan on Monday to try to resurrect efforts to end nearly 15 years of bloodshed in Afghanistan. They plan to meet again in Kabul on Monday.

“We are very keen to emphasize the urgency of having talks going in view of the need to be talking and getting a process going during the lull in the fighting season,” the senior official said.

He said the four countries had agreed that no Afghan groups would be excluded from the talks and that there would be no preconditions for joining.

“It’s clear that the Taliban have not yet decided to join the reconciliation process, but we are proceeding on the basis that we have to test the proposition,” the official said.

It was up to the Afghan government to discuss what incentives the Taliban could be offered, he said, adding there were indications the militant group wanted to avoid the international isolation it felt when in power before 2001.

Despite intensified battles, the Taliban had been unable to hold onto territory they had seized, the official said.

“It is by no means certain they necessarily can win on the battlefield,” he said. If the Taliban sought a degree of legitimacy, “that can only be achieved by them negotiating a place on the political table.”

On Tuesday, Afghanistan’s chief negotiator, Deputy Foreign Minister Hekmat Karzai, said he was hopeful the insurgents would join the process but warned that public support would wane if there were no quick results.

A previous round broke down in July after it became known that the Taliban’s founder and leader, Mullah Mohammad Omar, had been dead for two years and his deputy Mullah Akhtar Mansour had been in control.

The news badly damaged trust between Kabul and Islamabad, which many in Afghanistan believed had taken part in the cover-up, and set off a bloody leadership struggle within the Islamist movement.

A substantial faction led by Mullah Mohammad Rasoul has rejected Mansour’s authority. Militants close to Mansour have said they may consider joining talks, but so far Rasoul’s faction has ruled out any such efforts involving foreign powers.