Mozambican opposition leader Venancio Mondlane, who has been calling for protests for weeks in exile, said he would return to the country on Thursday.
Mondlane said he would arrive shortly before the new president's swearing-in next week.
Daniel Chapo of the ruling Frelimo party is scheduled to be sworn in next Wednesday after the court confirmed his election victory.
But Mondlane, the runner-up, rejected the result, sparking violent protests that have left dozens dead since October.
Mondlane left Mozambique in the same month, saying he feared for his life, after two of his aides were shot dead.
In a live speech on Facebook on Sunday, he sent a defiant message to the authorities, saying he “will be in Maputo. They don't need to chase me anymore.”
He said he would arrive at 08:05 local time (06:05 GMT) on Thursday at the international airport in Maputo, calling on people to welcome him there.
He said: “If they are killing my brothers… I will be there. You can do whatever you want. If you want to kill, kill. If you want to arrest, arrest too. I will be there.”
Mondlane asserts that he won the election and called for more protests until “electoral truth” emerges.
His supporters have often organized violent protests across the country to demand an end to Frelimo's 49-year rule.
He previously said he would do so Installing himself as president On January 15 – the day of the president's inauguration – despite the court upholding his rival's victory.
The Electoral Commission initially declared Chapo the winner of the election with 71% of the vote, compared to 20% for Mondlane.
The final official results issued by the Constitutional Court two weeks ago gave Chapo 65% and Mondlane 24%.
International election observers have previously said the vote was flawed, pointing to rigged numbers and other irregularities during the counting process.
Security forces sought to end the protests that spread across the country in a violent crackdown that tested the country's stability.
More than 270 people were killed, including demonstrators, children and members of the security forces, according to rights groups.
The unrest also affected the economy, with more than 12,000 people losing their jobs and more than 500 businesses vandalized.
Neighboring countries have also been affected by political unrest, with thousands of Mozambicans fleeing across the border.
Outgoing President Filipe Nyusi in the past called for dialogue to resolve the conflict. On December 27, Chapo called for “nonviolence” and “unity.”
