Kenya s defeated presidential candidate Raila Odinga speaks during a press conference at the Kenyatta International Convention Centre (KICC) in Nairobi on August 16, 2022. AFP
Ruto was declared president-elect on Monday, scraping past Odinga with a margin of less than two percentage points, after an anxious days-long wait for results of the August 9 vote.
The outcome has been challenged not only by Odinga's camp but also, in a bizarre twist, by four out of seven commissioners at the election body that oversaw the vote.
"We want to see justice done so that peace can be found," 77-year-old Odinga said at his Nairobi home after a meeting with religious leaders.
"We have decided to use the law to go before the Supreme Court and table our evidence to show that it was not an election but a joke."
The veteran opposition leader has now been defeated in all five presidential votes he has contested, even though this year he ran with the backing of outgoing President Uhuru Kenyatta and the weight of the ruling party behind him.
No presidential poll outcome has gone uncontested in Kenya since 2002, and the disputes have led to bloodshed in the past.
In August 2017, the Supreme Court annulled the election after Odinga rejected Kenyatta's victory. Dozens of people were killed by police in post-poll protests.
The aftermath of this year's court decision is being keenly watched as a test of democratic maturity in East Africa's richest economy.
Kenya's worst electoral violence occurred after the 2007 vote, when more than 1,100 people died in bloodletting between rival tribes.
Odinga -- or any other challenger -- has until 1100 GMT on Monday to file a petition at the Supreme Court.
The seven-judge tribunal will then have 14 days to issue a ruling. If it orders an annulment, a new vote must be held within 60 days.
"We are doing this to defend the democracy of our country that many people fought for," Odinga said.