Millions of Zimbabweans are expected to vote Saturday on a draft constitution that will for the first time limit the term of a president.

If the draft passes, it will replace the constitution written on the eve of the southern African country's independence from Britain in 1980 and paves way for the presidential and parliamentary elections later this year.

Under the draft, a president can only serve two five-year terms. But the new constitution is not retroactive, meaning President Robert Mugabe, already the eldest African leader who has ruled Zimbabwe since 1980, can remain on the top post until he turns 99.

It is the second attempt to change Zimbabwe's constitution. The first in 2000 failed after the majority dismissed a draft on the basis that it vested too much power in the president.

A civic group which played a major role in the rejection of the 2000 draft -- the National Constitutional Assembly -- is playing the same game again, urging Zimbabweans to reject the latest draft.

But most analysts expect a smooth passage of the draft as the text is prepared and agreed upon by the country's three major political parties, especially Mugabe's Zanu-PF and Prime Minister Morgan Tsvangirai's Movement for Democratic Change.

The electoral body, the Zimbabwe Electoral Commission (ZEC), has so far accredited close to 2,000 local and foreign observers for the plebiscite.

A total of 12 million ballot papers have been printed, with Harare taking the highest number of 1,749,000, followed by the Midlands Province with 1,600,000 ballots.

ZEC has established 9,456 polling stations and appointed 56,736 polling stations for the referendum.

Results will be announced within five days, the electoral body said.