Abuja: West African nations were preparing to send a high-level delegation to Ivory Coast after threatening force if Laurent Gbagbo refused to quit power.
Leaders from the 15-member ECOWAS regional bloc also warned on Friday in a statement after their summit that those responsible for post-election deaths would face international prosecution.
Gbagbo`s internationally recognised rival in last month`s presidential vote, Alassane Ouattara, meanwhile urged the Army to desert the incumbent leader.
The ECOWAS delegation was an "ultimate gesture" to Gbagbo in the hope that he could be persuaded to leave peacefully, said leaders of the Economic Community of West African States after an emergency summit in Abuja, Nigeria.
The leaders "expressed concern over the fast deteriorating political and security environment ... characterised by escalating violence, the use of mercenaries to perpetrate atrocities ... (and) the heightening ethnic tensions, as well the threat of a civil war."
If Gbagbo refused to heed ECOWAS calls to step down, "...the community will be left with no alternative but to take other measures, including the use of legitimate force, to achieve the goals of the Ivorian people," the ECOWAS statement said.
The bloc said it planned a meeting of military chiefs of staff from the organisation "to plan future action”.
Leaders also expressed "deep concern" over the deaths in recent weeks and warned "...all those responsible that they will face international trials for human rights violations at the earliest opportunity”.
At an emergency summit earlier this month, ECOWAS had already suspended Ivory Coast from the organisation and called on Gbagbo to step down.
Pressure on Gbagbo has mounted since last month`s vote, with the United States searching for more UN troops and France offering the incumbent president a final chance to step aside.
This latest summit was held after a UN body demanded a halt to "atrocities" in Ivory Coast and the Central Bank of West African States blocked Gbagbo`s access to finances following the World Bank`s earlier move to freeze loans.
The financial measures may make it difficult for Gbagbo to pay salaries for soldiers and others.
Gbagbo`s government spokesman Ahoua Don Mello branded the decision "illegal and manifestly outside the competence of the West African Monetary Union”.
He accused Ivory Coast`s partners of trying to disrupt what he claimed was the country`s return to economic normality.
Gbagbo has refused to budge in the face of escalating calls for him to leave, despite the fact that much of the world, including the United Nations, has recognised Ouattara as the winner of last month`s elections.
With Gbagbo unable to access the money to pay the troops, Ouattara made a direct appeal to the military on Friday, reading a statement from the Golf Hotel, the luxury Abidjan resort where his shadow government is holed up.
He and his colleagues are protected by 800 UN peacekeepers who are in turn blockaded by Gbagbo`s security forces.
French Foreign Minister Michele Alliot-Marie said Friday that Gbagbo could still step down honourably, but warned that time was growing short.