MONTREAL — A last-minute compromise between the United States and the European Communities broke a logjam Tuesday night to produce an agreement to protect the Earth's ozone layer.
"Very happy," declared Lee M. Thomas, administrator of the U.S. Environmental Protection Agency, after a tense day of negotiating. He said the United States will move quickly to ratify the pact.
The pact must still be formally approved by the 46 nations attending the U.N.-sponsored conference. The vote will come at a plenary session today. Once ratified, the pact would freeze consumption and production of chlorofluorocarbons by 50% by Jan. 1, 1999. Developing countries would have a 10-year grace period under the pact.
Chlorofluorocarbons, used in aerosols, refrigerator coolants and plastic foam, float into the stratosphere and attack the ozone layer.
The holes in the ozone, a 20-mile-deep belt of protective gas around the Earth, permit the sun's harmful ultraviolet rays to reach the Earth.
The United States is the world's largest producer, responsible for 30% of chlorofluorocarbons. It banned their use in aerosols in 1978, but the chemicals are more difficult to replace in other products.
A related group of chemicals, halons, used in fire extinguishing systems, causes up to 10 times as much damage to the ozone layer. Their production will be frozen in 1992 pending more research.
The U.S.-European compromise was proposed by New Zealand and was referred to Washington and Common Market headquarters in Brussels for political approval.
Thomas said he had been concerned about setting a precedent by recognizing the European Communities as an economic entity, rather than having the 12 member nations join the protocol individually. He said this would have left open the possibility that some of the Europeans might have ignored the treaty.
The impasse was broken with a special clause giving the Common Market overall responsibility, but only if each of the 12 members ratify the pact.
Within the market, Britain, France, Greece, Italy, the Netherlands, Spain and West Germany produce the offending chemicals.
The U.S. delegation compromised on another key issue. It first sought treaty ratification by nations responsible for 90% of the world's chlorofluorocarbons, but was ready to accept a figure closer to two-thirds, delegates said.