Opposition members of the Philippine National Assembly indicated willingness under certain conditions to contest a presidential election against President Ferdinand Marcos early next year even if he insists on remaining in office through the contest.

The members announced after a caucus that Marcos' attempt to circumvent the constitutional requirement of his resignation could be negotiable in a package of demands they are making. Officially, the opposition maintains that Marcos, in power for 20 years, must resign to run for reelection. His term runs until 1987.

Cecilia Munoz-Palma, an assemblywoman who is chairman of the opposition Unification Committee, said: "We have not closed the door" on the constitutional issue. "It is still open to certain conditions."

The opposition is to negotiate with Marcos' party when the assembly meets Monday after a brief recess. Marcos plans to submit his letter of intent to resign -- if defeated in the election -- together with a Cabinet bill mandating the special election. Marcos' party holds a two-thirds majority in the assembly. The opposition's assistant floor leader, Marcelo Fernan, said: "There are certain acceptable minimum standards we have to consider. We have to look at the whole package."

Marcos surprised the opposition Friday by announcing that he would resign as president but remain in office, as the resignation would only take effect when the winner is sworn into office.

The constitution says a special election can be held only in the event of a vacancy through death, incapacitation, impeachment or resignation. Marcos said his letter of intent to resign would create a vacancy about 15 days after the election, when the winner would take office.

The opposition said it plans to make 10 demands, with an independent electoral tribunal topping the list. Currently, the assembly proclaims the winner of an election. Fernan explained: "There is always the danger that if Mr. Marcos loses, he will tell parliament not to proclaim the winner."

Other demands include pushing the election date to March 17, antifraud safeguards, revamping the Commission on Elections and recognition of a citizens' election watchdog committee.