Frail Cuban leader Fidel Castro has stayed away from the opening ceremony of his 80th birthday celebrations in Havana on doctors' orders.
Castro appeared frail in his last TV appearance
A message apparently written by Mr Castro was read out saying he was not yet strong enough to attend the event.
President Castro underwent emergency intestinal surgery at the end of July and has not been seen in public since.
He then temporarily handed over power to his brother Raul, and was last seen in a video on 28 October.
Since falling ill, he has only been seen in officially-sanctioned photographs and videos.
Reports in the US suggest that officials in Washington now believe Mr Castro is suffering from terminal cancer and may never recover.
The birthday festivities had been originally scheduled for August but were postponed.
They were rescheduled around 2 December, the 50th anniversary of the day Mr Castro and others landed in Cuba to start a guerrilla movement and eventually seize power in 1959.
There is speculation that he will attend a military parade in the capital on Saturday to mark that anniversary.
Bolivian President Evo Morales and the Colombian Nobel laureate Gabriel Garcia Marquez are among some 1,500 notable guests heading to Cuba for the celebrations.
But if Mr Castro does not appear, many will wonder whether the president will ever return to power, says the BBC's Stephen Gibbs, in Havana.
Up to 5,000 people were packed into Havana's Karl Marx theatre when the president's note was read out.
In a note read from the stage to widespread applause, Mr Castro said his doctors had advised him not to appear before such a large crowd.
"It was only in the Karl Marx theatre that all guests could be seated but, according to the doctors, I was not yet ready for such a challenging engagement," he said.
Saturday's parade marks 50 years since Castro landed in Cuba
The note did not rule out the possibility that he might appear at other events planned for later this week.
But it did veer off onto a range of other subjects, including a brief criticism of US President George W Bush and the voicing of concerns over the state of the global environment.
Those in the hall gave the absent author of the note a rapturous round of applause.
"I sign off with the great pain of not having been able to personally give you thanks and hugs to each and every one of you," the note read.