ISLAMABAD (AFP) - Pakistan's fledgling peace talks with the Taleban suffered a fresh blow on Friday as a negotiator for the militants said he would take no further part until the agenda included the imposition of Islamic sharia law.

The intervention from firebrand cleric Maulana Abdul Aziz comes a day after teams representing the government and Tehreek-e-Taliban Pakistan (TTP) held a preliminary round of talks in Islamabad.

There has been widespread scepticism about the chances of the peace initiative achieving a lasting solution to the TTP's bloody seven-year insurgency.

Aziz, the chief cleric at Islamabad's radical Red Mosque, said Pakistan's constitution should be replaced by the Koran and the hadith, or sayings of the Prophet Mohammad.

"That should be the law in Pakistan and until the committee brings this point on the agenda I won't be part of negotiations," he told reporters on Friday.

He said he would remain part of the TTP's three-man delegation led by fellow cleric Maulana Sami-ul-Haq, unless told otherwise, but would not come to the negotiating table.

"I won't participate in talks until they include a clause about the imposition of Islamic law," he said.

On Thursday, the government and TTP negotiators, including cleric Aziz, issued a joint statement agreeing to work within the framework of Pakistan's constitution.

Cleric Aziz's move threatens to further undermine the talks - the government side has already voiced doubts about the composition and authority of the TTP's representatives.

The government delegation skipped an initial meeting on Tuesday, citing confusion over the militants' team after two members pulled out.