African Union Commission chief Jean Ping arrived in Abidjan on Saturday to give strongman Laurent Gbagbo and rival Alassane Ouattara a "message" from African leaders to avoid a civil war in Ivory Coast.
Ping was sent into the fray by a panel of African heads of state tasked with finding a peaceful solution to the dispute in which the two men claim to be president.
The violence has flared in the last two weeks, leading to fears that the unfinished business from last November's election could end up in civil war.
"Jean Ping arrived on Saturday morning with (AU) peace and security chief Ramtane Lamamra," said a source close to the African Union.
"They want to meet, successively, Laurent Gbagbo, Alassane Ouattara and Paul Yao N'Dre", president of Ivory Coast's constitutional council, he added.
International sanctions have been introduced against Gbagbo, who has refused to step down as president since November 28 elections, while Ouattara is internationally recognised as the west African nation's president.
The exact nature of Ping's "message" was not revealed.
However after a six-hour meeting in Mauritania on Friday, the presidents of Burkina Faso, Chad, Mauritania, South Africa and Tanzania demanded an immediate end to the killings in Ivory Coast and the lifting of a siege on Ouattara.
The five presidents also urged a halt to demonstrations that could "degenerate" into violence.
The leaders also said they would invite both Ouattara and Gbagbo to their next meeting, at a time and place to be announced.
Ping will be carrying their message when he meets the rival leaders.
Ministers in Ouattara's government said Friday they were planning a resolution at the UN rights council that refers to possible probes against Gbagbo by the International Criminal Court.
US Secretary of State Hillary Clinton has added her voice to calls for an end to the violence in Ivory Coast, accusing Gbagbo and his forces of a "callous disregard" for life.
Speaking soon after the African leaders called for an end to the killings, she said Washington "strongly condemns" attacks by Gbagbo's forces on his own people, including one Thursday on unarmed women demonstrators that left seven dead.
"Gbagbo and his forces have shown a callous disregard for human life and the rule of law, preying on the unarmed and the innocent. He should step aside immediately in the name of peace," she said.
Meanwhile aid agencies warned that the deteriorating situation in the country is stopping refugee workers and medical staff from helping those worst hit by the crisis.
The UN refugee agency said violence has forced it to halt plans for a camp for displaced people and suspend all activities in Ivory Coast.
Some 70,000 people had been displaced in the west, where there have been heavy clashes around the towns of Duekoue and Blolequin, UNHCR spokeswoman Melissa Fleming told reporters in Geneva on Friday.
The UN also said its experts were investigating suspected sanctions-busting arms deliveries from Zimbabwe to Gbagbo and "the arrival of light weapons cargoes from Zimbabwe" in December, the UN report said.
The panel of five presidents, put together by the African Union in January to seek a way out of the bloody impasse in Ivory Coast, originally had until the end of last month to come up with "binding" solution.
That deadline has since been pushed back to the end of March, illustrating not only the problems on the ground but the divisions between the five leaders on how to overcome them.
UN Security Council powers on Thursday expressed alarm at the Ivory Coast conflict "spiraling" toward civil war and called on peacekeepers to do more to protect civilians.
Gbagbo controls the armed forces, called the Defence and Security Forces (FDS), as well as Abidjan and the all-important cocoa exports.
Ouattara enjoys international diplomatic support and the backing of a northern former-rebel army, the New Forces, but has been unable to gain control of the key levers of state.