* Opposition says Isaias suffering from liver disease
* Asmara blames U.S. for spreading "lies"
By Aaron Maasho
ADDIS ABABA, April 23 (Reuters) - Eritrea has sought to quash speculation about President Isaias Afewerki's health, saying he was "fit as a fiddle" and lambasting the United States for spreading "lies" over his condition.
Rumours have been rife in the past few years that Isaias, 66 and in power since 1993 after leading his country to independence from Ethiopia, was in poor health and required regular trips abroad for treatment.
Speculation about his health has stirred up debate over who might eventually replace the reclusive leader. Isaias has no obvious successor but the opposition says he might be grooming his son, Abraham, for the top job.
U.S. diplomatic cables released by WikiLeaks have also mentioned the possibility of the military elite trying to take over power in the Red Sea state.
Eritrea refuted speculation about his health late on Sunday in a special announcement aired by the information ministry on state television and later broadcast on the Internet.
"There has been widespread speculation in the past few weeks that President Isaias has fallen seriously ill," the broadcast said.
"We would like to announce that President Isaias is fit as a fiddle and is in the best of health under all criteria," it added in remarks translated from the Tigrinya language.
Eritrea's exiled opposition has alleged on numerous occasions that the president is suffering from a serious liver ailment and that he has been receiving medical attention in Qatar, with which his nation has close ties.
In a move aimed at highlighting his good health, the broadcast showed a montage of Isaias sporting a baseball cap and making a short dash down a dirt track as he waved to bystanders in light rain.
It also pictured the leader snapping pictures with a point-and-shoot camera, then walking up a slope and posing as he smiled alongside other men on the banks of a reservoir.
Eritrea accused the U.S. Central Intelligence Agency (CIA) of spreading the "lies" surrounding its leader's health.
In a leaked cable from the U.S. embassy in the capital Asmara, former U.S. ambassador Ronald McMullen said Isaias feared the U.S. would try to kill him by firing a missile on his residence in the coastal city of Massawa.
Asmara often criticises Washington which it says backs its arch rival Ethiopia in the two countries' frontier dispute.
"Those lies emanate from Langley with the CIA being the rumour-mongers," said the television announcement, referring to the intelligence agency's headquarters.
Eritrea and Ethiopia have been at loggerheads since their 1998-2000 border war, which killed 70,000 people, and they accuse one another of backing the other's rebels and working to topple the other's government.
Isaias accused Washington last month of plotting Ethiopian cross-border raids that targeted alleged rebel camps. (Editing by George Obulutsa and Maria Golovnina)