The U.N. decolonization committee adopted a resolution today, over U.S. objections, whose effect could be to restore Puerto Rico to the world organization's official list of colonial territories.

The resolution, sponsored by Cuba and Syria, recommended that the General Assembly debate the status of the Caribbean "commonwealth" in 1982, for the first time in 29 years.

The vote was 11-to-2, with 11 abstentions and China not participating in the balloting. Australia and Denmark voted against the resolution.

The United States, which does not sit on the 25-nation committee and boycotted the four-day debate on Puerto Rico, sent a letter to the group's chairman reaffirming Washington's long-held position that U.N. consideration of the island's status is "totally improper," and interferes in the "purely domestic affairs of the United States."

The Assembly removed Puerto Rico from the U.N. list of non-self-governing territories in 1953, but the decolonization committee, composed largely of Soviet bloc and Third World nations, has nevertheless held annual debates on the territory for the last decade.

In recent years, the committee has also adopted resolutions calling Puerto Rico a colonial territory and urging the United States to transfer full powers to its people.

These committee decisions, however, are not binding on Washington or on the Assembly.

Under Article 73 of the U.N. Charter, colonial powers are obliged to make an annual report to the United Nations on conditions in non-self-governing territories on the U.N. roster.

U.S. officials contend that no such obligation would arise with respect to Puerto Rico until the Assembly actually calls for a report. But they are moving to forestall the possibility by lobbying against Assembly acceptance of today's committee resolution.

"Right now it is just a nasty nuisance," said one U.S. official, "but if the Assembly acts, it could become a political threat."