MANILA (Reuters) -- The main party in Philippine President Gloria Macapagal Arroyo's ruling coalition meets on Saturday to try to end differences over a planned change to the constitution and move to a parliamentary system.

Hours before the summit of Lakas (Strength) at the presidential palace in the evening, Arroyo was set to hold a private meeting with her most vital but unpredictable ally, former president Fidel Ramos, and three other party officials.

"Arroyo has agreed to a closed-door meeting with the former president to avoid embarrassments during the summit," said Ed Malay, a Ramos spokesman.

Ramos, unhappy at the direction of the planned reforms, sought another private chat with Arroyo and other party leaders ahead of the summit to further articulate his position.

His call for the president to cut short her term for elections for a new parliament in 2007 appears to have little support within the ruling coalition.

But is not without weight considering survey results showing more than half of Filipinos want Arroyo out before she is due to leave office in 2010.

On Friday, Ramos complained of conflicting versions in news media about his three-hour meeting with Arroyo and three others at her family's mansion in Manila on Wednesday evening.

Talking to supporters in his northern hometown in Pangasinan province, Ramos clarified a government statement he continued to support Arroyo's administration, saying he was working in the "national interest, not for particular leaders".

Ramos, a former general respected by many commanders and politicians, is seen as having saved Arroyo in July by standing at her side as other allies and much of her economic team deserted over allegations of vote-rigging and graft.

But he objects to plans by a commission, mostly picked by Arroyo, to cancel elections in 2007 for the two-house Congress and extend terms until a parliament is elected in 2010.

Ramos, 77, also criticized power-sharing proposals by some Lakas officials -- including an interim French-style system with a president and prime minister -- as preserving the "status quo for four more years".

Analysts say changes are needed to the political system, with its powerful families, vested interests, weak parties and often polarised debate that stalls law-making and reforms.

Earl Parreno, a political analyst, said he expected two agreements to emerge from Saturday's Lakas summit -- holding elections next year and changing the constitution to move to a parliamentary system.

Whether Arroyo finishes her term in 2010 would remain a contentious issue, he said, but Lakas leaders were expected to draw up a "happy compromise" to preserve the party's image as a united political machine.

"It all boils down to the transitory provisions in a proposed new constitution," Parreno said. "I am a bit disturbed because the real issues of governance, accountability and substance and form of the proposed parliament system would give way to debate on whether Arroyo would stay in office until 2010."

Beyond the president, the scope of the reforms could change the political futures of other lawmakers, including those positioning to try to become the country's leader.

There is also the question of whether the opposition would go along with reforms that did not include an early end to the president's term.

Arroyo's foes, united in wanting her out but otherwise split, failed with an impeachment motion last year and have not whipped up the public anger that ousted dictator Ferdinand Marcos in 1986 and Joseph Estrada as president in 2001.