Aides said opponents of the Gaza Strip pullout that Sharon championed and completed two weeks ago sabotaged the sound system, leaving the prime minister standing at the podium stern-faced and unable to be heard above the din at the Likud's Central Committee meeting.
The 3000-member group is to vote on Monday on a motion by Sharon's rightist challenger, former prime minister Benjamin Netanyahu, to bring the party's leadership election forward to November.
With violence surging on the Gaza border and sentiment strong in the Likud against the pullout that critics decried as a surrender to Palestinian armed groups, a primary in two months could be politically hazardous for the 77-year-old Sharon.
The prime minister got up to speak twice, but the microphone cut out before he could utter more than "good evening". After his second attempt to address the group, he left the stage.
"Someone tampered with the electricity and the microphone was cut off"
Sharon adviser Lior Horev
"Someone tampered with the electricity and the microphone was cut off," Sharon adviser Lior Horev said about the incident, which was broadcast live by Israeli television channels during evening primetime news.
Israel TV's Channel One quoted Likud spokesman Shmulik Dahan as saying someone had intentionally cut the power. Aides said Sharon would not return to address the committee
The committee vote could turn Israeli politics on its head.
As the group convened, Israel launched an air strike that killed a top Islamic Jihad commander in the Gaza Strip.
Earlier in the day, Sharon warned Palestinians of a crushing
response to rocket attacks from Gaza over the weekend.
Resistance groups said they launched the rockets at southern Israel in retaliation for a blast that killed 16 people at a Hamas parade on Friday, although Israeli and Palestinian Authority officials said Israel was not to blame.
The violence supported Netanyahu's charge that Sharon had not only betrayed the party by making one-sided concessions to the Palestinians but had endangered Israel's existence without giving the country anything in return.
Netanyahu accused Sharon of breaking promises to the voters and to Likud members by pulling out of Gaza and dismantling all 21 settlements there.
Benjamin Netanyahu said Sharon
had endangered Israel
"Hamas has taken control in the Gaza Strip and the Palestinian Authority has been wiped out," Netanyahu said.
"This is a move away from peace, which weakens the prospects of peace. It should not be our path," he added.
"There is another path which will reinforce our security and lead us towards peace: It is the path of Likud - protecting Jerusalem and the country."
Without mentioning Sharon by name, Netanyahu said: "Someone is threatening to leave us. Nobody threatens us ... . If someone wants to split, they better split now."
Sharon has declined to say whether he will remain in the party if the Central Committee vote goes against him, raising speculation that he may bolt and form a new centrist alliance that would tap into mainstream support for the Gaza pullout.
Surveys suggest a centrist alliance under Sharon, a former army general, would secure 76 of the Israeli parliament's 120 seats, while a Netanyahu-led Likud would fare badly.
"Hamas has taken control in the Gaza Strip and the Palestinian
Authority has been wiped out. This is a move away from peace"
Benjamin Netanyahu, ex-prime minister and Sharon challenger
"It is a move to impeach me," Israel Radio quoted from the speech Sharon was to have delivered to the committee on Sunday.
"I suggest everyone keep their cool. This is not the first time terror groups are trying to hit us ... We must talk less and act more. That's what we did in the past and that's how I'll act in the future," it quoted from the text of the planned address.
Sharon wants the party primary held closer to national parliamentary elections due by late next year and has said "radical extremists" have taken control of Likud, which he helped to found three decades ago.
Early primaries likely
A poll in the daily Maariv found 50.7% of the Central Committee planned to back Netanyahu's motion, and 42.3% were opposed.
Just 6.9% remained undecided, not enough, it would appear, to sway the vote in Sharon's favour.
Previous surveys had shown the result too close to call.
A Likud primary in November would almost certainly bring the
national election forward, perhaps as early as February.
Netanyahu quit as finance minister in Sharon's cabinet in August to protest against the pullout.