Negotiations on the issue of expanding the UN Security Council to 15 members are due to start on 19 February.
It was established after World War II and reflects the balance of power then.
The council has five permanent members, who have veto powers: the United States, Russia, Britain, France and China.
Ten members are elected on a regional basis who serve two-year terms before being replaced by others. They have no veto. Their number was set in 1965, after originally being six.
However, many diplomats believe there will be no quick outcome to the negotiations, due to regional rivalries and a concern by the big powers that their pre-eminence should not be diluted.
Numerous plans have been put forward in the past.