Ethiopia is entering the final stage of its transition from military rule to communist party rule and to formal entry into the Soviet camp. These revolutionary changes, which are to be implemented next September, were announced recently by Ethiopia's military leader, Mengistu Haile Mariam, at a meeting of the nation's only authorized political organization, the Commission for Organizing the Party of the Working People of Ethiopia (COPWE).
The new communist party will be called the Ethiopian Workers Party. Colonel Mengistu declared that ''in fulfillment of Marxism-Leninism principles,'' the new party will become ''the sole instrument to effect the realization of communism.''
If these plans are finally implemented, Ethiopia will become the first fully structured communist party in Africa - a prospect that its neighbors in the Horn of Africa view with alarm. (Two other African countries, Angola and Mozambique, profess to be Marxist, but do not have the Marxist structure that Ethiopia says it is adopting.)
The planning of these political structures in Ethiopia has been done in cooperation with several hundred Marxist ideological teachers provided by the Soviet Union and other East-bloc countries.
In preparation for the next stage of this revolutionary transition, COPWE has already established 240 basic organizations and 70 COPWE committees in the country's 33 provinces.
Colonel Mengistu also formally has declared Ethiopia's decision to enter the Soviet camp, which strongly anti-Soviet neighbors Kenya, Sudan, Saudi Arabia, and Egypt have feared.
Speaking of ''our spirit of proletarian internationalism'' and the need to strengthen the party's unity within the ''world socialist system,'' he added:
''This applies particularly to the relations we have established with the vanguard socialist country, the USSR, and with the rest of the socialist camp.''
In an earlier speech to COPWE, Colonel Mengistu compared Ethiopia's revolutionary role in Africa to that of Vietnam in Asia. He implied that just as Vietnam plays a revolutionary role in Southeast Asia, so Ethiopia would plan to do in Africa. He has said he would like his country to play a leadership role in support of revolutionary change on the continent.
In his latest speech, the Ethiopian leader denounced the United States for its policies of aggression and pledged active support for the peace efforts of the Soviet Union, which, he said, ''occupies the vanguard position among the forces struggling for the well-being of mankind in defense of the world socialist system, and to ensure global peace.'' (In early February, Ethiopia expelled four US diplomats. The US responded by ordering the expulsion of two Ethiopian diplomats.)
Mengistu's speeches to date make no direct reference to the extensive purge that is under way in Ethiopia. But the government has announced the arrest of 17 people accused of antigovernment activity in the capital.
''There is no doubt,'' Mengistu warned, ''that our enemies are terrified by the formation of our party because it will become the focus of the people's new political system of the future people's republic.'' The purge, which began a few weeks ago, has led to the expulsion of a number of top COPWE leaders and to the detention of an unknown number of prominent Ethiopians.
Ethiopia already enjoys observer status in the Soviet bloc's economic community, Comecon. But Colonel Mengistu has not yet revealed whether Ethiopia expects to become a full member. The only other third-world countries that are full members are Cuba and Vietnam. If Ethiopia joins, this would raise questions about its association with the European Community. Ethiopia is currently the largest single recipient of EC aid.