Ex-labor minister Blas Ople, one of Ferdinand Marcos' most loyal supporters, said here yesterday that he plans to return to the Philippines next week to head what is left of Marcos' political party and turn it into "constructive opposition" to the new president, Corazon Aquino.

The jockeying for that leadership, he said, will have to be settled in the next few months through a contest with other contenders. Chief among them, according to Ople, is Juan Ponce Enrile, even though Enrile has resumed his position as defense minister in Aquino's government. He was one of the two key figures in the mutiny that led to Marcos' ouster.

Ople arrived in Washington last week as Marcos' personal envoy. He said he was told to register concern about the direction U.S. policy appeared to be headed. The rebellion began in Manila hours after Ople's arrival.

At a lunch with reporters and editors of The Washington Post, Ople, 59, who managed Marcos' election campaign, appeared hopeful for a continuing role in politics and said he believed Marcos won the election, despite the charges of widespread fraud and violence. Marcos only lost his "moral authority," Ople said, when the ailing former leader was "overwhelmed by the passion of the anti-Marcos elements."

Ople, who served in Marcos' governments for 19 years and was his major speech writer, described the newly formed government as an "uneasy coalition" between the forces loyal to Enrile and the political organization now headed by Aquino. He described Enrile as "an accidental hero" who used to boast of his ability to deliver the vote for Marcos.

But Ople acknowledged that Aquino had the mandate and ability to govern and praised her new Cabinet members as "honest" and "competent." He warned, however, that unless Aquino made "palpable achievements" within six months, "people will start to question her authority."

In the battle against the growing Communist insurgency in the countryside, Ople said her election lent new credibility to fighting the New People's Army, the armed wing of the Communist Party of the Philippines.

"The guerrillas are like fish in ponds," he said. "Aquino is in an unsurpassed position to drain the ponds."

It is unclear what role Marcos' former ruling party, the New Society Movement (known by its Tagalog initials KBL), will have under the new government. It holds two-thirds of the seats in the National Assembly. Without the iron-fisted control of Marcos, many members of the party are likely to defect to Aquino's coalition, U.S. analysts said.

"This doesn't mean Mrs. Aquino should run a one-party state," said Ople, who said he wanted to build the party into a "guarantor of the democratic process" that could provide "constructive opposition."

Before Marcos fled the country, he chose Enrile as his successor to head the party despite Enrile's role in the mutiny, Ople said. "It doesn't mean the slate of two decades is wiped clean," Ople said, referring to the close relationship between Marcos and his former defense minister. "Marcos saw a situation in which Enrile could come to power."

Although Enrile declined the offer, Ople said, "Enrile would like to preserve the KBL as an opposition party to which he would have access." Both Ople and Enrile had been mentioned as possible successors to Marcos.