Washington — It is unlikely that Cuba supported or was the motivating force behind a reported coup in Grenada early this week. So say close observers in Barbados and the United States. The reported coup by Marxist hard-liner and Deputy Prime Minister Bernard Coard against his chief, Prime Minister Maurice Bishop, is instead a ''personal power play,'' these sources believe.
Radio Free Grenada broadcasts at the weekend suggested that Coard will allow Bishop to remain as prime minister, relegated to public functions, and Coard will be the island's real ruler.
Barbadan observers say they doubt Cuba is behind the Coard coup because any such Cuban role would be contrary to the Cuban line on Grenada, which has supported Bishop's policy of developing an economy that is partially in private and partially in public hands. Sixty percent of Grenadan enterprises are owned by the private sector.
It would not be in Cuba's interest to support a move toward radicalization at this time, observers say. In the past few months, Castro's regime, in an attempt to break out of its isolation in the region, has been attempting to woo leaders of Caribbean islands. According to these observers, this tactic has met with some success.
Nothing would alienate the British Caribbean more, Barbadan observers say, than a perception that Cuba supported the overthrow of Bishop's regime and of his attempt to find a radical but nonorthodox communist solution to Grenada's problems.
Reports suggest that Deputy Prime Minister Coard, far to the left of Bishop, has been pushing for a stepped up pace of radicalization in Grenada. With the support of the Army, he gained effective control of the country last Thursday when Bishop was placed under house arrest.
According to both close observers of the Grenadan situation in Barbados and US government officials in Washington, Coard and his military supporters have not officially deposed Bishop because of the strong popular support the prime minister still enjoys among average Grenadans.
There is no question that Bishop is a popular charismatic leader. Observers believe that Coard faces a real dilemma since although he may now enjoy Army support, he does not have that of the people. It is because of this that he has refrained from deposing Bishop outright, sources say.
On Saturday and Sunday, Radio Free Grenada broadcast a statement by Army chief Liam Omo Cornwall, Grenada's ambassador to Cuba, who was formerly a Bishop supporter. The statement criticized Bishop for placing himself above the party and attempting one-man rule. It stated that while Bishop would remain prime minister in charge of public affairs, Coard would handle all public affairs and in effect become the island's real ruler.
The statement also said that Bishop was being investigated for his responsibility in promoting ''lies'' that political divisions exist within the government and the party.
Shortly before Bishop's house arrest, Coard resigned his post as assistant prime minister in response to charges that he and his wife were plotting to assassinate Bishop.
As deputy prime minister, Coard was in charge of party mobilization, thus enabling him to build up his political base among Army officers and militants in the ruling New Jewel Movement. Barbadan observers feel that Coard took advantage of and exaggerated ''ideological'' differences with Bishop in order to gain personal power.
US government officials in Washington feel that this situation is still fluid but that if one were to choose between attributing Coard's move to outside influences or internal pressures, they would lead toward attributing it to internal pressures.
There was no indication that Bishop was about to depart radically from the Cuban line or that there was anything that would make the Cubans feel they had to get rid of Bishop.
President Reagan, perceiving Bishop as a leftist too much under the influence of Cuba, went on national television last March to complain about Grenada's ''Soviet-Cuban militarization.'' He pointed to a Cuban-built airfield in Grenada and suggested that it may be used to lift Cuban troops to Africa and elsewhere.