* Socialist president last seen in public a week ago
* Breaks silence with 90-minute phone call to state television
* Long absences raise speculation five months from election (Adds quotes)
CARACAS, May 18 (Reuters) - Venezuelan President Hugo Chavez ended a week-long silence o n Friday to say he was resting, following a diet and trying to tame his workaholic ways as he recovers from cancer treatment.
The usually garrulous and attention-seeking Chavez's disappearances from public view have become longer and more frequent this year. That has fueled speculation his condition has worsened and may complicate a re-election bid in October.
Allies in the ruling Socialist Party say the 57-year-old leader remains on top of government affairs and is not mulling a succession. Ch avez said he was working less than before his illness, but still about eight hours a day.
"Unfortunately, I can't carry on being the wild horse I was. I will rest and get well again," he said during the r oughly 90-minute ph one call, speaking in a firm voice an d twice breaking into song.
"I didn't used to sleep, now I'm working as the law dictates - just eight hours a day, resting, following a diet," the former soldier said. "I 've spent this week shut away here working ... I'll steadily be getting better."
Chavez has been seen only twice in public since mid-April, presumably under strict doctor's orders in his presidential palace. He made a half-hour appearance last Friday when he returned from Cuba after completing radiotherapy sessions.
Despite rumors he was wheelchair-bound, Chavez walked unaided down the airplane stairs and then inspected a military guard of honor.
Even on Twitter, where he is usually prolific and has a following of nearly 3 million people, Chavez has been uncharacteristically quiet.
The official line is that he is recovering from tough treatment and will soon be launching his campaign for the Oct. 7 election in which he is being challenged by state governor Henrique Capriles.
Chavez wrongly claimed to be "completely cured" at the end of 2011, so many Venezuelans are skeptical about his condition, especially given the plethora of rumors and leaks from pro-opposition media citing medical sources.
With the details of his health a state secret, all that is officially known is that Chavez has had three operations. Two malignant tumors were removed from his pelvic area.
The second was removed after what he called a recurrence of cancer this year.
The implications of a downturn in his health are enormous less than five months from the election, when Chavez hopes to extend his 13-year rule of the OPEC member. (Additional reporting by Mario Naranjo; Editing by Stacey Joyce)