A U.S. environmental delegation was ordered yesterday by the State Deparment to cancel an official mission to the Soviet Union, apparently as a reaction to the Kremlin decision to try dissident Anatoly Scharansky.

Departmental sources confirmed that the decision to cancel was made by Secretary Cyrus R. Vance, just hours before delegation leader Barbara Blum and two aides were to have left for the Soviet Union.

Blum, deputy administrator of the Environmental Protection Agency, was "asked" by Vance not to go ahead with the trip, according to her office. She planned to notify the Soviet embassy late yesterday.

Blum and her companions, Alice Popkin and Pierre Shostal, were to have reviewed progress being made in pollution-control and climatological research under terms of a U.S.-Soviet environmental agreement.

Popkin is EPA's associate administrator for international affairs. Shoscal research under terms of a U.S.-Soviet environmental agreement.

The State Department action came after some disagreement within the department. Sources said the U.S. ambassador in Moscow, Malcolm Toon, advised against the trip, but that officials here thought it should proceed.

Sources said that although Blum was "asked" by Vance not to make the trip, she was not given an option.

On another front, the White House indicated yesterday tha there has been no change in plans for another official U.S. scientific delegation to go to Moscow during the week of July 17.

That group, a joint commission on science and technology headed by presidential science adviser Dr. Frank Press, is charged with overseeing scientific exchange programs developed under the Nixon-Brezhnev detente agreements.