MANILA, March 28 -- After 17 years of on-and-off negotiations, the Philippine government and the Moro Islamic Liberation Front (MILF) finally signed Thursday the Comprehensive Agreement on the Bangsamoro (CAB) that both sides said would put an end to the decades-old conflict in Mindanao in southern Philippines.

The peace accord was signed by Miriam Coronel-Ferrer, chief government negotiator, and Mohagher Iqbal, MILF chief negotiator, at a ceremony held in Malacanang presidential palace.

President Benigno Aquino III, Malaysian Prime Minister Najib Razak, and MILF Chairman Al Haj Murad Ebrahim led some 1,000 congressional members, government officials, and foreign dignitaries in witnessing the signing ceremony.

In his remarks, Aquino said that the agreement stands as a testament on how far trust and earnestness can move humanity forward. "It shows how righteousness, reason and goodwill are the mightiest of instruments of ending conflict," he said.

Both sides said that they expect to finish the basic law for the Bangsamoro by March 31. The draft of the law that would officially establish the Bangsamoro, a political entity that would have some federal-type sovereign powers, will be submitted to the Philippine Congress for approval.

If passed, it will still be submitted to the people in the predominantly Muslim areas in Mindanao for their approval through a plebiscite.

Both the government and the MILF have said that the agreement will be the key to the peace, progress and development of Mindanao.

The peace accord is also aimed at ending an insurgency in Mindanao that has left an estimated 150,000 people dead since 1970s.

But realities on the ground may not bolster the optimism for peace of both the government and the MILF.

Nur Misuari, the acknowledged father of the Muslim rebellion in the Philippines, has vehemently opposed the peace accord.

Misuari, who founded the Moro National Liberation Front (MNLF), the forerunner of the MILF, claimed that the government has reneged on its promises set forth in the l996 peace accord signed by the MNLF and the government.

During the tenure of former President Fidel V. Ramos, Misuari signed a peace pact with government that resulted in the establishment of the Autonomous Region in Muslim Mindanao (ARMM). But after the signing, the group's top commanders, including Murad Ebrahim, who wanted a separate Muslim state, bolted out and formed the MILF.

Despite the emergence of the so-called splinter MNLF groups, Misuari is still a force to reckon with. In September last year, he ordered some 300 armed MNLF guerrillas to "invade" Zamboanga City just across the island province of Sulu, the MNLF's stronghold. It took the government about one month to end the siege of Zamboanga, leaving some 200 dead and thousands of city residents displaced.

Misuari has been charged with rebellion but he is still at large. Some of his followers say that he is just inside the country and could be planning another coordinated attack similar to what he did in Zamboanga.

Understandably, officials and residents of Zamboanga City, with only a few villages dominated by Muslims, are strongly against the plan to include them in the Bangsamoro.

Aside from the MNLF, the other "spoilers" in the quest for peace in Mindanao are the Bangsamoro Islamic Freedom Fighters ( BIFF), a renegade group of ragtag Muslim guerrillas led by Ombra Kato, a former top MILF commander, and the Abu Sayyaf, a terrorist group based in the island-province of Basilan in Mindanao reportedly linked to the Indonesian-based Jemaah Islamiyah and the Al-Qaida.

In the legal front, it is by no means smooth sailing for the peace pact. Former Senate President Juan Ponce Enrile, now the opposition leader in the Senate, has said that the peace agreement should be studied carefully because the proposed Bangsamoro entity may violate the territorial provisions in the Constitution.

Some groups have already expressed their desire to question the legality of the creation of Bangsamoro in the Supreme Court once its organic law is passed.

In 2008, the Supreme Court struck down as unconstitutional a similar version of the CAB, the establishment of the Bangsamoro juridical entity that was crafted by the government of then President Gloria Macapagal-Arroyo and the same MILF leaders.

Some analysts said that the rejoicing at the signing of the CAB could be premature because many things can still happen.

In its editorial Friday, the Manila Times, a leading daily in Manila, said that pragmatically, Aquino and his aides have made the MILF people believe that he could deliver what he had promised to them.

"Of course, he can't. We pray the result is not the MILF's feared eruption of violence, chaos and anarchy in Mindanao," the editorial warned.