“I am not physically able to speak directly to the citizens of the municipality where I was nominated for our elections next Sunday,” the ailing 81-year-old wrote in an essay published on Wednesday by state news media.

Castro’s latest essay focused on blasting US President George W Bush, but included references to the Cuban leader’s health.

It was published on the front pages of state-run newspapers a day after Castro met Brazilian President Luiz Inacio Lula da Silva, who said he thought Castro appeared healthy enough to return to politics. “I think Fidel is ready to take to take over his historic role in this globalised world,” Silva said.

Castro has not been seen in public since July 2006, when emergency intestinal surgery forced him to cede power to a government headed by his younger brother Raul.

Castro, however, expressed frustration in his essay: “I do what I can: I write. For me, this is a new experience: writing is not the same as speaking.”