In a move that will expand its access to one of the world's largest international telecommunications carriers, the Soviet Union yesterday signed a "memorandum of understanding" with Intelsat to formalize its relationship to the 109-member nation global satellite consortium.

However, neither the Soviets nor Intelsat indicated that the understanding would lead to full-fledged membership for the nation that is the largest nonmember user of the satellite network.

The understanding, which comes after seven years of negotiation, does lay the groundwork for increased use of Intelsat's network for global transmission of Soviet voice, data and television transmissions.

In March, sources said the Soviet Union was about to sign an agreement with the International Telecommunications Satellite Organization, or Intelsat, the Washington-based global consortium that provides telephone, telex and TV transmission to most of the world.

"They are motivated to join Intelsat," said Donald Latham, assistant secretary of Defense for command, control, communications and intelligence.

The Soviet Embassy declined comment on whether or when such an agreement would be signed.

If the Soviets increasingly use Intelsat, the reason will be to expand their broadcasting system to reach Third World countries, experts say. "It gives them a telecommunications link to the Third World they currently lack," Latham said.

Last year, the Soviets broadcast 441 hours of television programming over Intelsat -- representing 1 percent of the consortium's total television traffic. By contrast, U.S. use of Intelsat's television transmission capacity exceeded 6,884 hours -- 14 percent of the international television traffic.

Experts say that, because the Soviet Union tightly controls the domestic flow of information, there is no need for access to an international satellite system through which voice or data traffic could be channeled.

U.S. government sources also have speculated that Richard Colino, director general of Intelsat, may have used the threat of the Soviet Union joining the organization to deflect competition the cooperative was facing from entrepreneurs seeking to launch their own satellite systems.

The Federal Communications Commission just weeks ago authorized limited competition to the consortium. Months ago, a presidential decision determined that private launching of international satellites by the United States was in the national interest, but that the economic viability of the organization also must be protected. The State Department, Intelsat and Congress have worked on ways to protect the consortium.

Intelsat has denied using the Soviet Union to deflect competition, saying the Soviets initiated all discussions about agreements by inviting Colino and other top Intelsat officials to Moscow more than a year ago.

Intelsat, as an international organization, must accept the membership of any nation that belongs to the International Telecommunications Union, which includes the Soviet Union. "Intelsat has no authority to deny Intelsat membership to any union member nation," an Intelsat report says. "The Soviet Union is therefore free to move . . . to being a member-user nation of its own volition."

Intelsat has worked with the Soviet Union in the past and has coordinated its network of satellites with Intersputnik, the Soviet system, to prevent technical problems. The Soviets have used the Intelsat system on an as-needed basis.

Some government officials have said the Soviet Union might be interested in gaining technical information about the construction of satellites that could be used for military purposes.

The Pentagon's Latham said yesterday there is no military threat to the West if the Soviet Union becomes an Intelsat member. "The satellites and the technology are not going to be made