Malawi's Vice President Saulos Chilima and former president Joyce Banda have formed an alliance to take on the ruling party in May elections, a joint statement said Friday.
The opposition alliance does not include the Malawi Congress Party (MCP), which came second to the ruling Democratic Progressive Party (DPP) in the 2014 elections.
Mr Chilima has fallen out with President Peter Mutharika, and has teamed up with Banda and two other smaller parties ahead of the May 21 vote.
The alliance said it would reveal its presidential candidate on Monday, adding that "there are grounds for a united front among Malawians discontented with the sad state of affairs in this country."
President Mutharika won the last election defeating Ms Banda, who later fled after being embroiled in the multimillion-dollar "Cashgate" corruption scandal.
She returned to Malawi last year, saying the allegations against her were politically motivated. She has never faced any charges.
About half of Malawi's 18 million population live below the poverty line, according to the World Bank, and the country relies on foreign aid.
Food shortages, power outages and ballooning external debt have hurt Mutharika's popularity ahead of the vote.