(CNN) -- Some long-time Cuba watchers expressed skepticism Tuesday over a report by a former Mexican foreign minister that Communist leader Raul Castro removed two top-ranking officials earlier this month because they were plotting to overthrow him with the support of Venezuelan President Hugo Chavez. 

Fidel Castro, beset by illness, ceded power to his younger brother, Raul, pictured, last year. 

Jorge G. Castaneda, who served as Mexico's foreign minister from 2000 - 2003, wrote in the March 23 issue of Newsweek, which became public Saturday, that Deputy Prime Minister Carlos Lage Davila and Foreign Minister Felipe Perez Roque were concerned that Raul Castro would make concessions that would betray the 50-year-old Cuban Revolution. 

"For at least a month or so, Lage, Perez Roque and others were apparently involved in a conspiracy, betrayal, coup or whatever term one prefers, to overthrow or displace Raul from his position," Castaneda wrote. "In this endeavor, they recruited -- or were recruited by -- Venezuela's Hugo Chavez, who in turn tried to enlist the support of other Latin American leaders, starting with Leonel Fernandez of the Dominican Republic, who refused to get involved." 

The Venezuelan Embassy in Washington did not answer a verbal and written request for comment. 

The Dominican Republic Embassy in Washington did not answer telephones calls at various numbers. 

Robert Pastor, who served as a Latin America National Security adviser for President Jimmy Carter in the late 1970s, returned Saturday from a weeklong visit to Cuba. 

Pastor said he wrote Castaneda a letter upon his return expressing his disbelief in Castaneda's contentions. 
Who is Raul Castro?
Communist leader Raul Castro