A Soviet official negotiating with the United States on ways to verify two superpower treaties that limit nuclear tests said Saturday the talks would become "a milestone event."

The U.S. and Soviet delegations arrived in Geneva on Saturday for the third round of talks, which begin Monday after a two-month break.Both delegation leaders expressed hope the two sides would conclude protocols for verifying two treaties that limit nuclear tests to 150 kiloton explosions.

The verification, or anti-cheating, protocols under negotiation apply to the 1974 Threshold Test Ban Treaty and the 1976 Peaceful Nuclear Explosions Treaty. Both treaties were signed but never have been ratified, though both countries say they are abiding by the accords.

The United States has said it will not ratify the treaties until adequate provisions are made for verifying Soviet compliance with the pacts.