East-West: Nyet FOR SEPTEMBER

For months the speculation had been building, fed in part by Soviet officials themselves, that the United Nations 40th anniversary session in New York this September would provide the backdrop for an informal meeting between President Reagan and Soviet Leader Mikhail Gorbachev. But last week Armand Hammer, 87, chairman of the Occidental Petroleum Corp.. revealed in Moscow that he had been told by Anatoli Dobrynin, the Soviet Ambassador in Washington, that Gorbachev would not attend the U.N. session. The decision was later confirmed by a U.S. official in Moscow.

Hammer, whose numerous visits to Kremlin leaders began when he met with Lenin in 1921, also discussed a possible Reagan-Gorbachev summit during a 90- minute talk with the Soviet leader last week. Hammer said Gorbachev assured him that "there will be a meeting, just where and when has not been determined." But Gorbachev stressed that "to have a meeting we must meet about something -- something must be accomplished." Hammer said he had no doubt the two leaders would accomplish something when they finally did meet. "I think they'll like each other and be frank with each other," he said.