The United States and its anti-whaling allies today won a ban on the slaughter of killer whales by Soviet ships in the Antarctic and sharply reduced quotas of sperm whales killed by Japan in the north Pacific.

The two decisions, reached after a bitter debate that began Friday night and stretched into this morning, highlighted a week-long session of the 24-nation International Whaling Commission.

The quotas approved by the commission provided for 14,553 whales to be killed in the next 12 months. This is 9.2 percent less than the 15,883 killed this season.

In addition, conservationists said the ban on the slaughter of killer whales in the Antarctic will save the lives of at least another 1,000.

U.S. delegation chief Richard A. Frank said althoughh the commission had failed to adopt a U.S. demand for a worldwide ban on commercial whaling, reduced quotas will make it unprofitable to continue.

"We are close to reaching a point where quotas will be so low that it will not be economically viable to continue commercial whaling or worthwhile for whaling countries to face adverse publicity," he said.

He predicted commercial killing of whales may start being phased out within two years and halted altogether in three to five years.

Conservationists, who want to ban all whaling, complained the week-long IWC meeting did not adopt measures to protect the 80 or so species of smaller warm-blooded sea animals such as dolphins and porpoises.