MOSCOW, JAN. 5 -- The leaders of Comecon, formed 41 years ago as a Communist trade group, agreed today to disband next month as its members move to join the world economy.

The agreement signed by Comecon's executive committee after a two-day meeting at its Moscow headquarters was the result of the growing decay of centrally planned economies in the Soviet-led group.

Comecon members began trading among themselves with convertible currency Jan. 1, removing the main barrier to freer trade with the rest of the world.

The agreement to do away with the old Comecon and create a new, provisional organization to help the former Communist countries in the group convert to market economies is to be adopted at a final session on Feb. 27-28.

The nine-nation Comecon will be replaced by an association called the Organization for International Economic Cooperation. Its members will trade with each other and other countries "on a market basis," the Soviet news agency Tass said.

Most East European countries and the Soviet Union have expressed interest in joining the wealthy European Community. Czechoslovakia and Hungary have already applied for associate EC membership. The Soviet Union is seeking membership in the International Monetary Fund.