United Nations, N.Y. — Malaysia, representing many third- world countries, has put the question of Antarctica's future on the agenda of the United Nations General Assembly. Like the Law of the Sea Treaty, which took two decades of diplomacy, this first step could lead to Antarctica coming under new international regulations. At present, Antarctica is governed under a 1959 treaty adhered to by 16 nations with interests in the continent.
Malaysia and most other third-world nations do not claim that Antarctica is ''the common heritage of mankind,'' a phrase applied to the ocean. No major clash over Antarctica is expected this year at the UN.
''Malaysia has now taken a cautious first step; in a couple of years the UN may be chewing avidly on this new bone unless the club members show enough flexibility fast enough to make the treaty universally acceptable,'' says a diplomat from a European signatory to the treaty.
Members of the treaty ''club'' oppose UN interference in Antarctica, including a UN request that the Secretary-General conduct a study on the matter. The United States and the Soviet Union, despite the sore state of their relations, sent representatives together to see UN chief Perez de Cuellar and essentially recommended ''hands off'' the treaty.
The treaty's 16 members (12 of which signed the original pact in 1959 and were joined by four others since) include: Argentina, Chile, Australia, France, Belgium, Japan, New Zealand, Norway, South Africa, Great Britain, the US, the Soviet Union, West Germany, Poland, Brazil, India.
Chile, in strong opposition to the UN considering the question of Antarctica, claims the treaty:
* Effectively demilitarizes Antarctica and makes it a nuclear-free zone.
* Manages to maintain the ecological system.
* Already administers Antarctica for the benefit of mankind.
* Allows other countries to join the ''club.''
The 16 members also believe that those who have invested scientifically in Antarctica should be considered as ''pioneer investors'' and profit from it more than those - ''the Malaysias of this world,'' as one treaty member puts it - who have come late and simply clamor that they are entitled to a slice of the pie.
US companies in particular, which have a technological and financial advantage and which are expected to profit from Antarctica's riches, will be watching the UN proceedings intently.
Antarctica - larger than China, the US, and Mexico combined - is believed to hold large reserves of gold, copper, manganese, coal, possibly uranium, and definitely oil under its ice. But the continent is dark six months a year and temperatures go to minus 100 degrees F.
Seven of the ''consultative'' members of the treaty have laid territorial claims, of which three (United Kingdom, Chile, Argentina) overlap. The US does not recognize these. The treaty freezes the claims but does not determine who is to own and benefit from Antarctica's riches.
Singapore's UN ambassador, Tommy Koh, concedes that ''the treaty has worked well up to now.'' It has even promoted scientific cooperation and exchange of personnel among its members. It has prohibited the dumping of radioactive waste. ''But,'' he says, ''serious questions regarding Antarctica's fate and status deserve to be asked.''
He questions why treaty members meet in secrecy, and he asks why the treaty divides members into two classes: the more powerful ''consultative'' members and the ''acceding'' members.
US officials are eager to show that the treaty system is resilient enough to cope with new commercial and political pressures. A US diplomat believes the ''club'' must work more openly, relax its rules, and open up even more. Recently Brazil and India joined the club as full-fledged members. In order to co-opt third-world opposition, ''one can imagine Mexico, China, Nigeria being admitted as well in the future,'' he says.