NAIROBI (REUTERS) - Kenya's Supreme Court rules on Saturday on a legal challenge to Mr Uhuru Kenyatta's win in a presidential election seen as a test of democracy.

The country's outgoing president called for calm ahead of a decision that will either confirm the victory of Kenya's richest man Kenyatta or force another vote.

Defeated candidate Raila Odinga says the March 4 poll was marred by technical problems and widespread rigging. Both politicians have promised to abide by the court's final word.

"A country waits," a headline in the Nation newspaper read.

The court, by law, must give its ruling on Saturday but has not specified a time. At a final trial hearing on Friday, Chief Justice Willy Mutunga told lawyers to "keep your cellphones open" so they could be told when to gather.

Police formed a security cordon around the court. Many ordinary Kenyans insist they will not allow a repeat of the violence that killed more than 1,200 people and hammered the economy following a dispute over the last election in 2007.

"We have moved on," said Ms Monica Njagi, 28, owner of an Internet cafe in the port city of Mombasa. "Whatever the ruling, we shall go by it ... We have enough useful lessons from our past."

The peaceful voting this time round, and the fact that the dispute is being played out by lawyers rather than machete-wielding gangs, has already helped repair the image of east Africa's largest economy.

Saturday's ruling will test whether Kenyans trust their reformed judiciary and whether supporters of rival candidates accept the result quietly in a nation where tribal loyalties largely determine political allegiances.

"As the country awaits the Supreme Court ruling which is due this Easter weekend, I call upon all of us to accept the ruling and maintain peace," outgoing President Mwai Kibaki said in a message to mark the Christian Easter holiday.

Mr Kenyatta comfortably beat Mr Odinga in terms of votes won, with 50.07 per cent versus 43.28 per cent, but only narrowly avoided a run-off by just edging above the 50 per cent threshold.

Western donors are watching the fate of a trade partner and a country they see as vital to regional stability. They also face a headache if Mr Kenyatta wins.

He is facing charges at the International Criminal Court of crimes against humanity, accused of helping incite the violence after the 2007 vote. Mr Kenyatta denies the charges and has promised to cooperate with the court to clear his name.

Western nations have a policy of having only "essential contacts" with indictees of the court. They say that will not affect dealings with the Kenyan government as a whole, but will worry the issue could drive a long-time ally of the West closer to emerging powers such as China.

Neighbouring African states are also keeping a careful eye on proceedings after they were hit by the knock-on effects when vital trade routes through Kenya were shut down five years ago.

Kenya's economy has yet to fully recover from the pummelling it took after the vote violence, with growth rates still yet to return to levels before that bloodshed.

"My worry is that if the court orders another election, tourism will suffer further," said Mr Mohammed Hersi, general manager of the Whitesands hotel, a top Mombasa resort, saying clients were waiting to decide whether to come.

In the Supreme Court's hearing on Friday, the legal teams reviewed results of recounts ordered in 22 of the 33,400 polling stations after Mr Odinga said more votes had been cast than there were registered voters. Both sides said the recounts supported their arguments.

Mr Odinga's team argued that the failures undermined the vote.

Rival lawyers said any irregularities or technical hiccups had an insignificant impact and did not change the overall outcome.

International observers said voting itself was credible, but diplomats say observers did not watch the full five-day count.