South Africa's President Thabo Mbeki has been in the Democratic Republic of Congo for talks in an effort to keep the shaky peace process on track.
Mbeki is expected to discuss the insecurity in eastern DR Congo
Four people died in riots this week after indications the election scheduled for June might be delayed.
Members of the transitional government have also threatened to pull out of government if progress is not made.
Former colonial power Belgium urged DR Congo to keep to the schedule of the 2002 deal that ended five years of war.
Under the South African-brokered peace deal signed by all the main factions, a power-sharing government was tasked with organising elections.
"Any lack of clarity about the date of the elections will undoubtedly lead to some frustration," Belgium's Foreign Minister Karel De Gucht said.
Last year, Mr de Gucht sparked a diplomatic row when he questioned the ability of Congolese politicians to end corruption and facilitate a transition to democracy.
According to the BBC's Arnaud Zajtman in Kinshasa, Mr Mbeki shuttled between President Joseph Kabila's office and his hotel suite where he held separate talks with DR Congo's four vice-presidents.
Among them, vice-president and former rebel leader, Jean-Pierre Bemba, who has threatened to pull out of the government by the end of January if the issue remains unresolved.
It is estimated some three million people died in the war
Last week, elections chief Apollinaire Malu Malu indicated the poll will probably take place in October, before heavy rains make parts of the country inaccessible.
But this has not gone down well with the electorate, anxious to participate in the country's first democratic elections since independence in 1960.
Protests continued this week. On Wednesday morning violent demonstrations took place in Mbuji Mayi, an opposition stronghold in the centre of the country.
UN chief Kofi Annan said in a report last week that there were "serious challenges" to holding the election in June.
The UN has also expressed concerns about the logistics of holding an election in a country which is so large yet lacks basic infrastructure, such as roads and railways.
Further fighting in eastern DR Congo last month - involving former Rwanda-backed rebel soldiers - highlights the challenges the transitional government faces, correspondents say.
It is an issue expected to be discussed by President Mbeki and his Congolese counterpart.
At a summit of African leaders on Monday, the African Union resolved to help the country in disarming and neutralising militias linked to Rwanda's 1994 genocide.