The ODM had earlier said that there would be a delay in announcing the government, citing disagreements over posts in the cabinet of what is expected to be Kenya's first constitutional coalition government since its 1963 independence from Britain.
"The two leaders are meeting and we are waiting to see if the cabinet will be announced today," Alfred Mutua, a government spokesman, told the AFP news agency on Sunday.
"The ongoing consultations on the formation of a cabinet are going on very well."
According to a separate government statement, PNU is to cover the finance, defence, foreign affairs and justice portfolios, while ODM is to take others including roads, public works and tourism and agriculture.
Both sides are trying to implement a February 28 deal, which has already been enshrined in the constitution, to end tribal fighting and revenge killings that erupted following disputed December polls which Odinga accused Kibaki of rigging.
The violence killed at least 1,500 people and displaced hundreds of thousands.
Yvonne Ndege, Al Jazeera's correspondent in Kenya's capital Nairobi, said the sticking point was the key ministerial positions of finance, local government, energy and internal security.
She said that Kenya was on a "knife edge" and that there was a huge amount of public anger over the size of the cabinet which could be one of the "biggest in the world".
The delay is a major setback in the implementation of a deal reached on February 28 to end the violence that erupted following December's election, which Odinga accused Kibaki of rigging.