Joao Bernardo Vieira was in power for more than 20 years
Guinea-Bissau cannot afford to hold elections following the assassination of its president earlier this month, Cape Verde's prime minister says.
Cape Verde is helping co-ordinate efforts to restore order in its fellow former Portuguese colony.
According to the constitution, polls should be held within 60 days.
Joao Bernardo Vieira, in power for more than two decades, was killed by soldiers hours after the military chief was killed in a bomb attack.
The speaker of parliament has been sworn in as interim president until elections can be held.
Guinea-Bissau has a long history of coups and instability.
Its institutions have been made even more fragile since the country became a major hub for trafficking cocaine from Latin America to Europe.
The BBC's Alison Roberts in Portugal's capital, Lisbon, says this week Lusophone countries agreed on the need for an international inquiry to find out who was behind the assassination of the country's president and armed forces chief.
Next month Cape Verde is next month to host a roundtable to discuss what support to offer Guinea-Bissau.
"Twenty days have gone by, so 40 are left, but neither the logistical nor the financial conditions are in place to fulfil this constitutional deadline," Cape Verde's Prime Minister Jose Maria Neves said in Lisbon.
Mr Neves said the priorities were bolstering the interim president's powers and paving the way for elections in June or November - either before or after the rainy season.
The political class in Guinea-Bissau and Cape Verde know each well, as they fought together against Portuguese rule in the 1960s and '70s.