September 28, 1984

Walter F. Mondale accused President Reagan today of an ''inexcusable'' attempt to shift the blame for last week's bombing of the American Embassy near East Beirut. Earlier, the White House sought to soften Mr. Reagan's implication that the fault lay with the ''near destruction of our intelligence capability'' before his Administration took office. At a news conference after his meeting in New York City with Andrei A. Gromyko, the Soviet Foreign Minister, Mr. Mondale asserted that Mr. Reagan should quit trying to pass on the blame for the incident. ''The latest statement by the President is inexcusable,'' Mr. Mondale said. ''He should stand up and say he is responsible. By saying the C.I.A. is weak, he encourages terrorists and our enemies around the world to believe that we don't have an effective intellignce capacity, when we do.''

NEW YORK is the only city in America, and one of the few in the world, with two major opera companies. Yet for reasons of scheduling, tonight, tomorrow and Sunday mark the first weekend in nearly a year that the Metropolitan Opera and the New York City Opera are offering simultaneous performances. In the past, the Met ran from September to April - it still does - and the City Opera gave two half-seasons, one in the fall and one in the spring. But in 1982, Beverly Sills, the general director of the City Opera, announced her intention to consolidate the company's two seasons into one summer-fall season, running from early July until mid-November. Her plans were frustrated the first year, in 1983, by an orchestra strike, although the City Opera and the Met did perform together last fall. This year, the City Opera has been operating at full tilt since July, but the Met only swung back into action Monday, with Placido Domingo, Anna Tomowa-Sintow and Eva Marton in Wagner's "Lohengrin."

THE unprepared visitor who walks into the Museum of Modern Art any time between now and Jan. 5 may be startled to find that a large part of the museum has been taken away from modern art. In its place, we find primarily a community of vagabond spirits that originated quite some time ago in Africa, Oceania and the Americas. The spirits in question inhabit the standing figures, the reliquary figures, the fetishes, the headdresses and, above all, the masks that fill room after room. Irrespective of their date, place of origin or primary function, these objects have a presence, a fierce contained energy and a robust conceptual approach to the human form. They were not conceived as likenesses of something else, but as themselves. For the most part, they are shown in a subdued light, as if what they have to say to us were confidential, and when we look at them, we are at once thrilled and disoriented, awed and a little alarmed. Such eyes, such noses, such a superabundance of hair and such chain-saw teeth have rarely come our way.

At exactly 8:30 Friday morning, the Government will publish what might seem to be its most important economic statistic: the figure designed to predict the course of the $3.6 trillion-a-year American economy. Whether the 21-month old economic expansion is slowing down, stalling out or perhaps even slipping into recession is of overwhelming interest to business planners, stock and bond operators, consumers, workers and economists, not to mention politicians with eyes fixed on Election Day. The leading index for August is expected by many economists to eke out a small gain, mainly the result of a very strong stock market last month. But it could also fall slightly, thereby producing a third consecutive decline, which is popularly regarded as a sign of impending recession.

Sweeping organizational changes were announced yesterday by AT& T Information Systems, the company formed to market computers, phone switching systems and other advanced office equipment for the deregulated American Telephone and Telegraph Company. The reorganization, the second in two years, came amid reports that the company has been unable to fashion a winning market strategy. In an announcement from its headquarters in Morristown, N.J., AT& T Information Systems said it would be divided into three divisions - one to serve large corporations, a second to serve small and mid-sized concerns as well as consumers, and a third to manufacture computers that it would then sell to retailers or supply to the two other groups. The key to the reorganization, the company said, is that each of the new divisions will have capabilities in research, manufacturing and marketing. Until now, AT& T Information Systems has been mainly a marketing arm, with development and assembly of products kept separate.