One of Nigeria's main opposition leaders has condemned his party's decision to join the government.
Muhammadu Buhari denied that his party had deserted him
Muhammadu Buhari told the BBC he was "extremely disappointed" by the decision of "part" of his All Nigeria People's Party (ANPP).
The ANPP has lodged legal challenges against its defeat in April's elections, saying they were rigged in favour of the ruling party.
President Umaru Yar'Adua took power in May but has not named his ministers.
Mr Buhari told the BBC's Network Africa programme that the ANPP had said that no election had taken place.
"How can part of the party go and talk to the government?" he asked.
"They are just looking for jobs for themselves."
He denied that he had been deserted by his party, saying he wished well to those who had joined the ruling People's Democratic Party.
But the BBC's Senan Murray in Abuja says most ANPP officials, including current and former governors, are behind the move to join the government.
Election observers had said Umaru Yar'Adua's victory was not credible
But he says most ordinary opposition supporters are against it.
It is not yet clear how many ministerial posts the ANPP has been offered.
As well as challenging the outcome of the presidential vote, ANPP candidates have also gone to court over the results of parliamentary and governor elections.
International observers said the election had been "not credible".
Mr Buhari, a former military ruler, said he had not wanted to attend the talks called by Mr Yar'Adua.
After two days of talks, both parties agreed to work to address issues including the electoral process and the constitution.
Mr Yar'Adua has said he wants to address Nigeria's pressing problems - including poverty, unrest in the oil-rich Niger Delta region and violent crime.
Mr Yar'Adua received 24.6 million votes in the election compared with some 6.6 million for Mr Buhari, according to official results.
The May polls were the first time one elected administration had handed over to another in Nigeria's history.
The country was ruled by a succession of military leaders until 1999.