The court on Tuesday declared unconstitutional the draft accord to grant minority Muslims expanded self-rule in their southern homeland in a bid to end decades of separatist rebellion.

Violence in the southern Mindanao region flared up in August, leaving nearly 100 dead and half a million displaced, after Christian politicians protested the planned signing of the accord and rebels went on a bloody rampage.

The government then abandoned the deal, suspended peace talks and launched an offensive to punish three rebel commanders blamed for the attacks.

Mohagher Iqbal, chief negotiator for the Moro Islamic Liberation Front, said the only option left for the rebels was to take the accord to the United Nations and the Organisation of the Islamic Conference to seek their guarantees that if talks resume their outcome will be respected.

'We will bring it to a forum where the voices of the Moros will be heard,' he said.

He criticised President Gloria Macapagal Arroyo's government for backing out of the deal after 11 years of negotiations, and said militants within the rebel ranks who are opposed to the peace process may stage fresh attacks.

'After long years, we came to a point that seemed to bolster what the anti-negotiation groups are saying: that the government could not be trusted,' Iqbal said.

The rebel group - with an estimated 11,000 fighters - has been battling for self-rule in the predominantly Roman Catholic nation's volatile south for decades.

Despite the latest setback, both sides said they will respect a 2003 cease-fire, which has been monitored by a handful of international observers.

US and Philippine officials had hoped a peace accord would transform the resource-rich southern Philippines into a bustling economic hub instead of a breeding ground for terrorists. -- AP