Jakarta, Indonesia (CNN) -- Indonesia's presidential candidate, Prabowo Subianto, who slammed the country's election commission and rejected the official results of the vote held earlier this month, appears poised to launch a legal challenge.
A member of Prabowo's legal team said they plan to file a complaint against the election commission at the Constitutional Court on Friday. The court has until August 21 to make a ruling.
His opponent, Joko "Jokowi" Widodo, won Indonesia's presidential race with 53% of the votes over Prabowo's 47%, the country's election commission announced on Tuesday.
Hours before the release of the voting results from ballots cast on July 9, Prabowo criticized the election commission, citing what he called "massive, structural and systematic cheating." In his speech carried live, he declared: "We withdraw ourselves from the process."
His statement drew confusion and uncertainty.
But on Wednesday, his brother and business tycoon Hashim Djojohadikusumo said, "Let me be clear, Prabowo never withdrew as a candidate for president."
He said they would have accepted the results, whether the former lieutenant-general won or not, if they believed the vote count was fair.
"We continue to have grave concerns about the integrity of the electoral process in a number of provinces," his brother said. "An estimated 52,000 polling stations have reported irregularities, putting an estimated 21 million votes in question. The indication of massive fraud and widespread irregularities is overwhelming."
Congratulations for Jokowi
Meanwhile, congratulations from the United States, Singapore, Malaysia and other nations poured in for Indonesia's president-elect.
Widely known as "Jokowi," he has drawn comparisons to Barack Obama for his unlikely ascent, from growing up in humble origins to becoming a national politician.
On Tuesday, he delivered a speech aboard a traditional Indonesian boat, calling for national unity in the world's most populous Muslim nation.
"I ask you to heal your relations within your family, with neighbor to neighbor and with friends that were once broken."
The new president will be inaugurated on October 20.
CNN's Kathy Quiano reported from Jakarta, Indonesia and Madison Park wrote from Hong Kong. CNN's Jason Hanna contributed to this report.