FACTBOX: How does Zimbabwe's vote verification work?

HARARE (Reuters) - Verification of Zimbabwe's disputed presidential election results is due to start on Tuesday, a month after the vote, and the country may learn within a week whether Robert Mugabe will remain in power.

Here are some details on how the verification process works:

WHAT'S HAPPENED SO FAR?

Since the March 29 elections, the Zimbabwe Electoral Commission (ZEC) has counted and recounted the presidential votes cast across the country and collated results from the ward level up to the provincial level.

At the same time, opposition parties have collected their own statistics directly from the nearly 9,000 polling stations.

WHAT DOES THE VERIFICATION PROCESS ENTAIL?

From Tuesday, the ZEC is due to invite candidates, their agents and observers to verify the results compiled by the ZEC ward by ward.

Verification entails comparing the official ZEC figures from every ward with those of political parties. Parties are obliged by law to take part.

If there is a query or a candidate disputes a particular figure, the ZEC must produce a "V11" form which was signed by members of political parties and ZEC officials at polling stations and confirms a given tally.

Only after all parties agree with the figures from the verification exercise can the ZEC announce a final result.

Utoile Silaigwana, the ZEC's deputy chief elections officer, said on Monday the verification could take up to a week because some of the results were likely to be disputed.

HOW IS THE WINNER DETERMINED?

If a candidate has more than 50 percent of the vote, he is automatically declared winner.

If no one has a majority, the ZEC will announce the final result and immediately call a run-off between the top two candidates within 21 days from the day the result is announced.

(For full Reuters Africa coverage and to have your say on the top issues, visit: africa.reuters.com/)

(Reporting by Harare bureau; Writing by Caroline Drees)