Foreign ministers from Brazil, Germany, India and Japan have failed to reach a deal with the African Union on rival bids for UN Security Council seats.
A successful bid to change the council needs two-thirds majority
However, the ministers, known as the Group of Four, and their African counterparts pledged to continue talks later this week.
The Group of Four have put forward a resolution calling for six more permanent seats on the council.
Brazil's foreign minister said the resolution needed African support.
Brazil's Celso Amorim, Germany's Joschka Fischer, India's Natwar Singh and Japan's Nobutaka Machimura met with an 18-member AU delegation that included the foreign ministers of Nigeria, South Africa and Libya, and Egypt's deputy foreign minister.
All are aspirants for permanent council seats and hope for a UN General Assembly vote on enlargement of the 15-member body at the end of the month.
The Group of Four ministers want 10 new seats on the council. Six of those would be permanent, including two for Africa.
The African resolution calls for a total of 26 seats on the council, and for the new permanent members to have veto rights.
To win any vote in the general assembly, the Group of Four needs the votes of the African bloc.
During the meeting, the two sides "discussed the differences in a frank way and expressed a determination to overcome the differences", Mr Amorim said.
The Security Council is criticised for reflecting the world of 60 years ago rather than the current situation.
Permanent members of the powerful council are China, France, Russia, the UK and the US.