Lt. Col. Mengistu Haile Mariam, now more firmly in the saddle as the country's strongman after a bloody abortive coup yesterday, told a crowd of 200,000 supporters today that he would arm "progressive elements" to protect the country's "socialist revolution."

In a vaguely worded speech he also called for the creation of a workers party and said there will be no more attempts to compromise with opposition groups.The speech in the capital's main square gave no details, however, on what role the workers party would play in the government or who the armed "progressives" would fight.

Mengistu said the country was surrounded by enemies. Among the enemies he named within the country were the extreme leftist Ethiopian People's Revolutionary Party, the rightist Ethiopian Democratic Union and the Eritrean liberation forces and their foreign supporters.

The Addis Ababa government has suffered reverses in recent weeks both from the Eritreans in that rebellious northern province and from a kind of EDU forces in the northwest.

Mengistu struck an uncompromising stance today and said there would be no further attempts at negotiating with the rebels.

"How could we possibly negotiate with our enemies? Revolutionaries and counter-revolutionaries cannot eat together," he said.

The huge crowd was orderly but spirited and many waved banners and Ethiopian flags. Some banners attacked "American imperialism" while other said that Sudanese President Jaafar Nimeri will "meet his doom" for his support of the Eritrean rebels.

There were few regular security forces in the main square with order maintained mostly by guards from the newly formed urban dwellers associations. These groups have repeatedly demanded that they be armed to counter the spate of political assassinations in recents weeks at the hands of far leftists.

Mengistu has now promised to arm the urban groups, a step taken in the past only in rural areas.

In today's speech, Mengistu said that Ethiopia has no friends among its neighbors, except for South Yemen.

"Saudi Arabian royalists and Sudanese anti-Communist reactionnaries" are in league with the EDU and the Eritreans against the Ethiopian revolution, Mengistu charged.

Mengistu did not announce who would be the new chairman of the military council and the head of state. The two previous chairmen, Gen. Aman Michael Andom, executed in November 1974, and Brig. Gen. Teferi Bante, killed yesterday, were outsiders to the ruling council until their appointment. It is not known whether another outsider will now be brought in or whether Mengistu, now first vice chairman, will take the position, Col. Atnafu Abate, the second vice chairman, was away from the capital at the time of the shootout yesterday. He returned this morning but did not attend the rally.

The military council has sought with little success for two years to establish the image of Ethiopia as a revolutionary country and to lessen its dependence on the West for military and economic aid.

His actions brought a message today from Cuban leader Fidel Castro saying that he would watch closely the progress of the Ethiopian revolution. The Soviet ambassador met with Mengistu this afternoon.

While Ethiopia has been undergoing enormous economic and social upheaval over the past two years and most actions are cast in the rhetoric of revolution, yesterday's bloody abortive coup mainly appears to be another upheaval in the ongoing power struggle among the military rulers, rather than an ideological struggle. Many observers believe that the power struggle is far from completed.

Diplomats said today that Mengistu appeared to be trying to rally workers and students to his side. There has been increasing criticism of military rule from both quarters as well as calls for a return to civilian rule.

Ethiopian Radio today said that Mengistu had discovered a plan to overthrow the military government and install the Ethiopian Peoples Revolutionary Party and said that Teferi Bante and the other rebels killed yesterday belonged to the party.

The government announced today that three Mengistu supporters were killed in yesterday's violence, in addition to Lt. Col. Daniel Asfaw, a member of the ruling council whose death was annouced yesterday. The deaths announced today were of Sennaye Likey, a civilian closely associated with Mengistu, and two soldiers.