Fidel Castro has said he doubts he will make it to the end of Barack Obama's four-year term as US president and has instructed Cuban officials to start making decisions without taking him into account.

In an online column titled Reflections of Comrade Fidel, the 82-year-old former Cuban president suggested his days were numbered, saying Cuban officials "shouldn't feel bound by my occasional Reflections, my state of health or my death".

"I have had the rare privilege of observing events over such a long time. I receive information and meditate calmly on those events," he wrote. "I expect I won't enjoy that privilege in four years, when Obama's first presidential term has ended."

He didn't elaborate, but the lines had the ring of a farewell.

"I have reduced the Reflections as I had planned this year, so I won't interfere or get in the way of the [Communist] Party or government comrades in the constant decisions they must make," he wrote.

Castro stepped down in July 2006 to undergo emergency surgery and hasn't been seen in public since. He turned over the presidency to his younger brother, Raùl, in February last year after nearly half a century as Cuba's leader, but his periodic essays have continued to carry weight.

They are diligently read in full at the top of midday and nightly radio and television newscasts before any other national or international story. At times, they have even appeared to contradict the words of his brother, prompting speculation over who is really in charge.

Yesterday's essay came out on a government website shortly before the nightly news, but newscasters chose not to mention it, instead reading a column Castro had released on Wednesday.

The bulk of yesterday's column was devoted to praising Obama, the 11th US president since the Cuban revolution, in part for his decision to close the US prison at Guantànamo Bay in Cuba.

Castro recalled his thoughts as he watched Obama assume the "leadership of the empire".

"The intelligent and noble face of the first black president of the United States ... had transformed itself under the inspiration of Abraham Lincoln and Martin Luther King into a living symbol of the American dream," he wrote.

Castro praised Obama as honest, writing: "No one could doubt the sincerity of his words when he affirms that he will convert his country into a model of freedom, respect for human rights in the world and the independence of other nations."

However, Castro suggested Obama would succumb to threats greater than his own qualities: "What will he do soon, when the immense power that he has taken in his hands is absolutely useless to overcome the unsolvable, antagonistic contradictions of the [US] system?"

Obama has said he will not end the US embargo on Cuba without democratic reforms on the island, but will ease limits on Cuban-Americans' visits there and on the money they send home to relatives. He has also offered to negotiate personally with Raùl Castro.

Before Castro's latest two columns he hadn't been heard from in more than a month, fuelling rumours that he had suffered a stroke or lapsed into a coma. Those rumours were dispelled on Wednesday when he met the Argentininian president, Cristina Fernandez, the first foreign leader known to have done so since 28 November.

Fernandez said Castro wore the tracksuit that has become his trademark since he fell ill.

Raùl Castro, 77, said on Wednesday that his older brother spent his days "thinking a lot, reading a lot, advising me, helping me".

In an interview published yesterday by the Russian news agency Itar-Tass, Raùl Castro said Cuba would insist that the Obama administration close the entire US naval base at Guantànamo Bay – not just the prison camp for suspected terrorists.

"We demand that not only this prison but also this base should be closed and the territory it occupies should be returned to its legal owner – the Cuban people," Castro was quoted as saying, repeating a long-standing demand.