LONDON, Oct. 18--Russia tonight accused the United States of urging Turkey to launch an invasion of Syria along a 180-mile front and offering the active help of the American 6th Fleet.

Tass, Russian news agency, said it had been authorized to make the statement. This means in effect that it was issuing an official declaration of Soviet policy.

U.N. to Debate Syrian Charges

UNITED NATIONS, N.Y., Oct. 18--The United Nations agreed tonight to a full-scale debate on Soviet-Syrian charges that Turkey and the United States are plotting to touch off war in the Middle East.

By a vote of 66-0 with a single abstention--Liberia--the 82-nation Assembly approved a recommendation of its Steering Committee that it take up the Syrian complaint that a threat exists to Syrian security and also to world peace.

Diplomatic Break

BONN, Germany, Oct. 18--Chancellor Konrad Adenauer's government will break diplomatic relations with Communist Yugoslavia tomorrow, diplomatic sources said tonight.

The Big Three Western allies were reported backing West Germany in the decision to retaliate in this fashion for President Tito's recognition Tuesday of Red-ruled East Germany.