UNITED NATIONS The mandate of the UN commission that will probe the 2007 slaying of former Pakistani premier Benazir Bhutto will not exceed six months and will not extend to conducting a criminal investigation, according to a UN letter released Thursday.

In a letter to the UN Security Council, UN chief Ban Ki-moon, said that after extensive discussions with Pakistani authorities and members of the Security Council, 'it has been agreed that the international commission should be fact-finding in nature and that its mandate would be to determine the facts and circumstances of the assassination.'

'The duty of determining criminal responsibility of the perpetrators of the assassination would remain with the Pakistani authorities,' Bans letter said.

The UN secretary general made the announcement on the independent panel Wednesday at a banquet hosted by Pakistani President Asif Ali Zardari.

Pakistan had called for a UN commission to probe the assassination of the two-time prime minister who was killed at a campaign rally, after her supporters were angered by conflicting accounts from the then-government of how she died.

UN sources said the UN enquiry panel was likely to be headed by Chiles UN Ambassador Heraldo Munoz.