The abrupt postponement of the summit meeting of the Group of 15 developing countries this month suggests members may be confused about their future, but that does not mean Third World unity has disintegrated, analysts here say.

The Indian government announced the summit scheduled for Dec. 13-15 had been postponed because only four heads of state had confirmed their participation. Under the group's rules, a minimum 10 is necessary for a summit.Official sources said the summit is being tentatively rescheduled for March.

Analysts here said the postponement should be seen in the larger context of recent world economic and trade developments.

"It's possible most countries have not been able to make up their minds on the new (economic and trade) groupings, and whether a combination like the G-15 can serve them better in the long run or become a weight," said D.L. Sheth, director of the Center for Study of Developing Societies.

Members who didn't want to attend probably are trying to buy time for themselves so issues troubling them can be discussed, he conjectured.

The G-15 was launched in 1989 during the ninth non-aligned summit in Yugoslavia. It comprises Algeria, Argentina, Brazil, Chile, Egypt, India, Indonesia, Jamaica, Malaysia, Mexico, Nigeria, Peru, Senegal, Venezuela and Zimbabwe.

The aborted summit was scheduled to discuss such issues as dialogue with the Group of Seven major industrialized countries, South-South cooperation, trade, economic and development issues and the role of the United Nations and its restructuring.

While some Indian officials privately acknowledge the postponement is a ''humiliation" for the country, the government's spokesman insisted the ''postponement should not be looked upon as an indication of a lack of commitment to the grouping's goals.

"It is an unfortunate coincidence of events which prevented a number of heads of state and government from attending the summit," he said.

Mr. Sheth noted there are ups and downs even in groupings like the European Union. But, he warned, if by the next summit the heads of state are not clear about their objectives, "definitely it will be downhill" for the group.

A.P. Venkateswaran, former foreign secretary and now with a think tank called the Center for Policy Research, said there may be a perception that world economic and trade developments are making the G-15 redundant or at least less purposeful.

"Larger forces are at work. There is a tidal wave for globalization," he said, citing the North American Free Trade Agreement, the recent Asia-Pacific summit in Seattle and the Uruguay Round trade pressures.

Other analysts said the postponement is a reminder that idealism no longer suffices to sustain cooperation between economies.

The G-15 is a diverse set of countries with widely differing development indicators and disparate geo-political alliances and interests.

"One can doubt whether the summit, had it taken place, would have amounted to much," said one analyst.

Looking ahead, the Hindustan Times newspaper commented: "If G-15 has been rendered partially irrelevant today, it need not cause a heartbreak. What is of paramount importance for countries like India . . . is to develop or strengthen (regional) blocs or seek entry into a community on the basis of mutual benefit."