Three new islands in Southeast Asia Have been identified as possible centers for large numbers of Indochinese refugees, with at least one of them ready for use in "a matter of weeks," a high ranking State Department official said today.

Discussion of the centers came up during Secretary of State Cyrus Vance's talks Monday and today with the foreign ministers of the Association of Southeast Asian Nations. The Asian officials are holding their annual meeting near here on the resort island of Bali. The Association members say that they are being inundated by the refugees and the issue has dominated their meeting.

The State Department official declined to say which islands meight be used but said two of them are in Indonesia and the third is in the Philippines. They are in addition to Indonesia's Galang Island which the Jakarta government offered earlier this year. Surveys indicate Galang could handle only a small fraction of the refugees.

The source said that because of international commitments made in recent days financing of the island refuges is no longer in doubt.

"The money is going to be there," he said. "That is not a problem."

Location of temporary island refuges for the thousands of Vietnamese boat people is regarded as the key to limiting the loss of lives as the key to limiting the loss of lives as more refugees come out in small boats and are turned away by Thailand, Malaysia, Singapore, and Indonesia. The Philippines is the fifth member of the association.

The most crucial country, Malaysia, has long indicated it might relax its tough policy of pushing off refugee boats if there were assurances that the people on board would be moved quickly from its shores to a processing center somewhere else.

Until recently no island has been available that could accommodate large numbers of refugees. Galang, technicians say, could become home for only about 10,000 refugees. About 60,000 boat refugeos arrived safely from Vietnam in May and thousands more are believed to have drowned that month.

The State Department source said that the two other Indonesian islands and one in the Phiplippines will be surveyed quickly to determine whether they could be supplied with enough water, food and housing to take care of large numbers.

The source said one of the Indonesian islands under consideration is large enough to accommodate "tens of thousands" of regugees and that one or all of the three could be ready to accept people "in a matter of weeks, not months."

Officials are apparently reluctant to divulge the three islands's locations because of the fear of arousing opposition amount local residents.

The islands centers are expected to become temporary refuges for boat people either picked up at sea or thrust away from shorelines of Asian nations. They would be cared for in the centers until permanent resettlement is arranged in other countries.

Secretary Vance's promise of international financing for the centers was part of a growing effort to convince the Southeast Asian nations that they will soon be able to resettle the refugees quickly. In turn, Vance asked the Asian foreign ministers to urge their governments to stop forcing refugee boats back out to sea and, in the case of Thailand, to stop pushing Cambodian refugees back into their war-torn country.

No promises were made by the foreign ministers, according to informed sources, but Vance was described as being optimistic that he had won some support. Saturday the five nations reemphasized their determination to push boats back to sea and to coordinate sea patrols for that purpose.

American officials said the next step in a process which began at the Tokyo summit meeting last week will be the major international gathering of some 60 countries in Geneva on July 20 and 21. Its primary goals are more funds for refugees and more opportunities for their permanent resettlement.

U.N. Secretary General Kurt Waldheim is coordinating that conference and he is attempting to enlist support from many nations, including some in Latin American and the Middle East, which so far have offered little assistance.

It now appears likely that Vietnam will not attend the Geneva talks, according to American officials. Several countries have urged Vietnam to establish its own processing camps so that refugees can leave in an orderly flow that would minimize loss of life. Vietnam has said it would agree to an orderly departure of 10,000 a month but so far no procedures have been established and refugees are still coming out in a haphazard fashion, U.S. officials said.

Secretary Vance left Indonesia today for Canberra and the annual meeting of the ANZUZ defense pact that links Australia, New Zealand and the United States. The Indiochinese refugee question is expected to dominate those talks als.