September 27, 1983

President Reagan, calling on the Soviet Union ''to reduce the tensions it has heaped on the world in the past few weeks,'' today offered what he described as concessions aimed at advancing the deadlocked Soviet-American talks on medium-range nuclear missiles in Europe. Speaking to a packed General Assembly chamber at the opening of debate in this year's session, Mr. Reagan charged that the Russians had violated arms and other agreements in the past, but declared that the United States was prepared ''to be flexible in our approach, indeed, willing to compromise,'' to win weapons agreements now. 'Door to Agreement Is Open' ''The door to an agreement is open,'' the President told the delegates, speaking of the medium-range missile talks. ''It is time for the Soviet Union to walk through it.''

With trumpets flourishing fanfares on a picture-perfect New York autumn evening, the Metropolitan Opera, America's largest, grandest performing-arts instituton, opened its centennial season last night. ''It's pretty exciting,'' said Anthony A. Bliss, the company's general manager. ''It's hard really to take in the fact this is the 100th anniversary.'' Placido Domingo, the Spanish tenor who, after some cliff-hanging indecision, went ahead and sang for the first time the difficult part of Aeneas in Berlioz's five-hour epic, ''Les Troyens,'' said: ''Opening night is always an event. All the people have come back from vacation, and they are excited to see opera again.''

An article in Business Day yesterday incorrectly identified an advertising copy writer who occasionally contributes to The National Lampoon.

Santa Fe Industries and the Southern Pacific Company, owners of two of the largest railroads serving the Western half of the nation, asked that trading in their stock be halted yesterday, amid widespread expectation that they would announce a newly negotiated merger. Spokesmen for the two companies declined comment. Al Bradshaw, a spokesman for Southern Pacific, which is based in San Francisco, said he expected the company to make an announcement today. A spokesman for Santa Fe, Robert Gehrt, said his company's board was meeting this morning in Tulsa, Okla., and any announcement would probably be made then.

A limited experimental program to control acid rain is now ''crystallizing'' at the Environmental Protection Agency and is receiving particular attention from the agency's Administrator, William D. Ruckelshaus, according to agency officials and others with whom he has discussed the issue in recent days. But even this limited approach, which would cost $1.5 billion to $2.5 billion and is one of several that have been suggested, has drawn criticism from the Energy Department and the Office of Management and Budget as premature and too costly, these officials reported, thus causing a delay in reaching a decision. No decision has been made as to whether the program would be paid for by the Federal Government, state governments, private industry or a mix. It would require substantial reductions in sulfur dioxide from power plants and factories in Ohio, Pennsylvania, West Virginia and New York, with some reductions in Vermont and New Hampshire and possibly Indiana and Michigan.