Venezuelan President Hugo Chavez will return to Cuba for medical treatment, months after he received chemotherapy for cancer there.
The 58-year-old, who was re-elected for a fourth term in October, has made regular trips to Cuba since he was diagnosed with the disease in June 2011.
He celebrated his election win in front of thousands of supporters on a balcony of the presidential palace and had appeared to be making a good recovery.
However, he has not been seen in public for almost two weeks and has been absent from Twitter , where he has not posted a message to his 3.7m followers since November 1.
Mr Chavez revealed his travel plans in a letter to Venezuela's National Assembly.
He wrote: "Six months after I completed the last radiation therapy treatment, it has been recommended that I begin a special treatment consisting of various sessions of hyperbaric oxygenation.
"Together with physical therapy, (this) will consolidate the process of strengthening my health."
Mr Chavez was given permission to travel to Cuba by his country's Congress, and was expected to make the journey on Tuesday.
Hyperbaric oxygenation involves breathing pure oxygen while in a pressurised chamber, according to Macmillan Cancer Support .
The charity said it is most commonly used to treat the side effects of radiotherapy, which affects blood cells and vessels and can cause changes in the oxygen supply to body tissues.