CAIRO (Reuters) - Choosing a possible successor to Egypt's President Hosni Mubarak, 81, is not on the agenda for a ruling party conference this weekend, a party official said, despite silence on the issue fueling speculation it might be.

Mubarak, who has run Egypt for 28 years and will address the National Democratic Party conference that began on Saturday, has yet to say whether he will run in the 2011 election.

His politician son Gamal, 45, a top party official, is tipped as the most likely candidate to lead U.S.-ally Egypt after his father leaves office, although father and son have denied any such plans.

Safwat el Sherif, the National Party's secretary-general, poured cold water on the idea that a decision could come this weekend, saying selection of a presidential candidate could only occur at a special party meeting.

"We have a special conference to choose the party's candidate in which the name would be put forward to the special conference, which is not held annually, and choosing the party's candidate for the presidency would be its one and only subject," he said, adding this was based on the party's rules.

His comments were made to a television programme and reported by the official news agency MENA.

Hala Mustafa, an Egyptian analyst and member of the party's policy committee, told Reuters the issue of a presidential candidate would more likely be on the agenda next year.

"There is still a lot of debate regarding the next candidate mainly because the president did not say whether he will run or not. He had in the past said he will lead until his last breath which gave the impression that he might re-run," she said.