The State Department has cleared the way for American Telephone & Telegraph Co. to use Soviet communications satellites to open 100 new phone lines between the United States and Soviet Union.

The tie-in would be the first permanent one between a U.S. long-distance company and the Soviet Intersputnik satellite system.

The department earlier had opposed the plan on the grounds that it would improperly divert business from Intelsat, the 119-nation consortium that handles most of the world's international satellite communications, and threaten its economic viability.

Opening more international lines is an important part of Soviet efforts to spur economic development. Between 1987 and 1989, calling between the United States and the Soviet Union on the AT&T network rose 140 percent. But many would-be callers get busy signals because there are only 130 satellite lines available for all long-distance companies.

The Soviet Union uses Intelsat even though it's not a member, but had proposed using its own satellite system for new lines so as to reduce the foreign exchange it would have to pay.

The deal must now be approved by the Federal Communications Commission. However, State Department opposition had been viewed as the only serious obstacle.

The State Department dropped its opposition, citing a recent decision by Intelsat that if other satellites carried 100 lines or fewer it would be too small to pose an economic threat.