A 112-nation conference aimed at phasing out chemicals responsible for depleting Earth's protective ozone shield opens with a boost from Western countries that want chlorofluorocarbons eliminated by the end of the century.

Environment Secretary Nicholas Ridley said he hoped the three-day conference beginning Sunday would persuade more countries to follow the lead of nations that have endorsed the elimination of CFCs.Britain initially hoped to get the conference to agree to an 85-percent reduction of CFC use by the end of the century.

The goal is more ambitious than that outlined in the Montreal Protocol, an international treaty requiring signatory nations to cut CFC use to 50 percent of 1986 levels by 1998. About 30 nations, including the United States, have ratified the pact.

The 12-nation European Community agreed Thursdyy to eliminate all CFC use by the year 2000.

Kenyan President Moi is slated to give the opening address at the "Saving the Ozone Layer Conference."

Prime Minister Margaret Thatcher, who believes tackling ozone depletion is the most achievable of the major environmental goals, will deliver a speech. Prince Charles, who long ago banned aerosols in his home, will make a personal plea.

Of the 150 nations invited, 112 will attend, including China, South Korea, Vietnam, Pakistan, Uganda, Tanzania, Venezuela and the Soviet Union. India is the only major nation that had not accepted.

Because environmental degradation respects no country's boundaries, global agreement is essential, Ridley said. "You can't solve the problems unilaterally. You have to solve them internationally."

Sen. Albert Gore, D-Tenn., who is attending the conference, said a phase-out of CFCs is a good first step, but the chemicals must be banned within five years, as called for in his pending legislation.