Factbox-What are the key steps in Sri Lanka's presidential election process?

COLOMBO (Reuters) - Sri Lanka's presidential election will be held on Saturday with 38 candidates vying for the debt-ridden South Asian nation's top post.

Here are the key steps in the process in which 17.1 million Sri Lankans are eligible to vote for their next president, who will serve a five-year term.

NOMINATIONS

Sri Lanka's election panel approved the nominations of 39 candidates, including President Ranil Wickremesinghe, for the vote. One candidate later died.

CAMPAIGN RALLIES

Official campaigns began after the election panel approved the candidates. Wickremesinghe's rally on Aug. 17 in the historic city of Anuradhapura was the first of about 100 he has held. His key rivals also held dozens of rallies each.

END OF CAMPAIGNING

Campaigning for the election ended at midnight on Wednesday, 48 hours before election day.

NUMBER OF ELIGIBLE VOTERS

Over 17 million voters are eligible to participate in the election. About 1 million of them are first-time voters.

ELECTION PROCESS

Sri Lanka's first-past-the-post system allows voters to choose three candidates, with the candidate securing at least 50% or more of the overall vote declared the winner.

If no candidate gets 50% in the first round, there is a legal provision for a run-off between the two frontrunners. For the first time in four decades since the introduction of the current voting system, Sri Lanka could see a second count given the close race between the frontrunners.

VOTING AND COUNTING

Votes are set to be cast in thousands of polling stations amid tight security. They will be counted by government employees after polling ends, supervised by Election Commission officials, election monitors and representatives of candidates.

Voting begins at 7 am local time (0130 GMT) and ends at 4 pm (1030 GMT) with counting scheduled to start shortly after.

DECLARATION OF RESULTS

The Election Commission will formally announce the winner, probably on Sunday. The winner will then take the presidential oath, usually on the same day, and appoint a new cabinet of ministers.

(Reporting by Uditha Jayasinghe; editing by Sudipto Ganguly and Miral Fahmy)