MANILA, Philippines - Philippine President Gloria Arroyo will not be able to achieve her aim of ending a decades-old Muslim rebellion before she steps down in June, the government's top peace negotiator said Tuesday.

Arroyo has backed years of tortuous negotiations in between outbursts of violence in the southern Philippines, but a "comprehensive compact" that she had wanted is beyond her reach, negotiator Rafael Seguis told AFP.

"A final peace treaty under this present administration will not be possible for obvious reasons," Seguis said.

He said demands made by the Moro Islamic Liberation Front (MILF) negotiators "will require legislative action or constitutional changes".

Congress has already adjourned ahead of the May 10 elections, when 50 million Filipino voters are due to elect a successor to Arroyo and candidates for thousands of other, lower posts.

Parliament is due to sit again only on the last Monday of July, when the new president will make his or her traditional "State of the Nation" address to lay out the new administration's key policies.

However, the 12,000-member MILF had already said after the end of the last round of talks in Malaysia last week that the two sides remained "deadlocked," and that it was not looking to sign any permanent deal with Arroyo.

Nevertheless, Seguis said the peace process was not dead in the water, stressing that the government would continue peace talks with the rebels in Kuala Lumpur.

In the absence of a final peace treaty, he said the Arroyo government was aiming for an "interim peace agreement" with the MILF.

He said an interim accord would preserve terms that had been agreed so far between the two sides, chiefly a ceasefire and conflict resolution mechanisms.

The separatist rebellion on the southern island of Mindanao has left more than 150,000 people dead since 1978.

Arroyo said when she became president in 2001 that she was determined to end the conflict with the MILF before her time in power came to an end.