HAVANA (Reuters) - President Barack Obama is trying to make positive changes in the United States, but is being fought at every turn by right-wingers who hate him because he is black, former Cuban leader Fidel Castro said on Tuesday.

In an unusually conciliatory column in the state-run media, Castro said Obama had inherited many problems from his predecessor, George W. Bush, and was trying to resolve them. But the "powerful extreme right won't be happy with anything that diminishes their prerogatives in the slightest way."

Obama does not want to change the U.S. political and economic system, but "in spite of that, the extreme right hates him for being African-American and fights what the president does to improve the deteriorated image of that country," Castro wrote.

"I don't have the slightest doubt that the racist right will do everything possible to wear him down, blocking his program to get him out of the game one way or another, at the least political cost," he said.

Castro, who writes regular commentaries for Cuba's state-run media, has criticized Obama, complimented him occasionally and said that he is watching him closely to see if he means what he says about changing U.S. policy toward Cuba.

His latest column comes during a visit to Cuba by New Mexico Governor Bill Richardson that has stirred speculation that he may try to push U.S.-Cuba relations forward.

Richardson has been a diplomatic trouble-shooter in nations with which the United States has poor relations. In 1996 he negotiated with Castro for the release of three Cuban political prisoners.

Obama has said he wants to end 50 years of hostilities between the United States and Cuba and has eased the long-standing U.S. trade embargo against the communist-led island.

But he has said the embargo will be lifted only if Cuba shows progress on political prisoners and human rights. Cuban President Raul Castro has said he is happy to discuss these issues but will make no unilateral concessions....