Ivory Coast's incumbent leader Laurent Gbagbo is insisting he is the true president of the country, but said he would be willing for an international committee to re-examine the election results.
In a speech broadcast on state television Tuesday, Mr. Gbagbo defied a global barrage of criticism, saying he won the November election.
However, he said he did not want more bloodshed in his country and offered to allow envoys from world powers, including the African Union, the United Nations and the European Union, to form a panel to study the post-election crisis.
The international community has recognized Mr. Gbagbo's rival, Alassane Ouattara, as the winner of November's disputed poll.
U.N. Secretary-General Ban Ki-moon warned Tuesday that Ivory Coast faces "a real risk" of return to civil war.
He accused forces loyal to Mr. Gbagbo of trying to blockade the U.N. mission there and said the situation could become critical within days. He appealed to U.N. member states to help supplies reach the mission, which is guarding a hotel serving as headquarters to Mr. Ouattara.
The U.N. chief said there has been an alarming increase in violence in the past week and said the United Nations has confirmed that mercenaries are being recruited from neighboring countries.
The United Nations say more than 50 people have been killed in recent days and says it has received hundreds of reports of people being abducted from their homes by armed assailants in military uniforms.
Nigeria said Tuesday it evacuated families of diplomats serving in Abidjan because of the intensifying standoff. Reuters news agency quotes Nigeria's Foreign Minister Odein Ajumogobia as saying the Nigerian embassy in Abidjan was attacked.
In another development, the United States Tuesday imposed travel sanctions against Mr. Gbagbo and his supporters, following a similar move by the European Union on Monday.
U.S. officials say the travel sanctions are only the opening move in an international campaign that will steadily ratchet up the pressure on Mr. Gbagbo to accept the election results and leave the country.
West African leaders plan to hold an emergency summit Friday to discuss the political crisis in Ivory Coast. The Economic Community of West African States has already recognized Mr. Ouattara as the winner of last month's election and called for the Mr. Gbagbo to step down.
On Monday, the United Nations extended its peacekeeping mission in Ivory Coast for another six months, defying a demand from Mr. Gbagbo that the troops leave immediately.
The U.N. refugee agency says the tension and instability have prompted about 6,000 Ivorians to flee to neighboring Liberia, with another 200 going to Guinea.
The presidential election was meant to restore stability to Ivory Coast, which is trying to recover from a 2002 civil war that left it divided into rebel and government-controlled areas.