Ariel Sharon's Likud party has narrowly rejected a move to force him into a leadership contest against Binyamin Netanyahu.
According to an exit poll, 51% of members of the right-wing party's central committee voted against the proposition with 49% calling for the primary to be moved forward from April 2006.
However, the TV poll has a 4% margin of error.
Mr Netanyahu, a former prime minister, was hoping to force Mr Sharon into a November leadership contest in a bid to capitalise on resentment within Likud over the recent pullout of troops and
settlers from Gaza.
Mr Sharon wants to hold off any move to bring forward a ballot, in order to allow time for the scars left by his disengagement plan to heal.
Earlier, Hamas announced it was ending rocket attacks on Israel from the Gaza Strip.
Up to 40 rockets had been fired at Israel in recent days, weeks after its military withdrawal.
In response, Israel has resumed its policy of targeting militant leaders in air strikes.
Announcing the end to the attacks, the Hamas leader in Gaza, Mahmoud Zahar, said the organisation was committed to a ceasefire which militants declared earlier this year.
