The Soviet Union today bitterly countered Reagan administration charges that Moscow supports international terrorism by accusing the United States of global subversion and assassinations.

In a commentary, the official Tass news agency and U.S. ingelligence services had assassinated or overthrown foreign political leaders such as the Congo's Patrice Lumumba, Chile's Salvador Allende, Iran's Mohammed Mossadegh, attempted to kill Cuba's Fidel Castro, and were implicated in the assassinations in the United States of president John F. Kennedy, his brother, Robert Kennedy, and civil rights leader Martin Luther King Jr.

The vitriolic response indicates that Secretary of State Alexander Haig stung the Soviets badly by accusing them in his first press conference last week of "training, funding and equipping" international terrorists.

The Tass rebuttal seemed esspecially aimed at bolstering Soviet attempts to gain influence in Iran and El Salvador, concentrating on alleged U.S. backing of repressive governments in those countries. It declared that "terrorism as a means of attaining political aims is deeply alien to the Soviet Union."

Instead, Tass said, "the tracks of the criminals lead to the United States . . . . U.S. leaders themselves [back] the granting of a free hand abraod, meaning the elevation of terrorism to the rank of state policy."

The commentary did not attack Haig of President Reagan by name, speaking only of the "U.S. administration."

Tass claimed that "in the United States itself, terrorism as a means of attaining political goals has become a daily practice. The ruling circles of the U.S. are making wide use of it not only for the physical elimination of undesirable politicians, but also for the suppression of dissidents. It is enough to recall the murder of the Kennedy brothers, of King, and many other participants in the antiwar and democratic movement."