Some African states oppose sending peacekeepers to Burundi without its consent after it said that would be seen as an invasion, Gambia's president said on Saturday at the start of an African Union summit.
Rifts in Africa about whether to deploy the 5,000-strong force will worry Western powers and others, who fear Burundi will slide into ethnic conflict if there is no intervention.
The African Union's peace and security council announced the plan for the force in December, but Burundi swiftly rejected it.
The AU charter allows a force to be sent against the will of a host country if there is a risk of serious violence, such as genocide. But some African leaders may be concerned about setting a precedent that could be turned on them, experts say.
"It is not only Burundi that is resisting that idea," Gambia's President Yahya Jammeh told reporters at the AU headquarters in Addis Ababa when asked if there was opposition to the plan for peacekeepers. He did not name any nations.
Asked if Gambia was among them, he said: "Without the consent of Burundi, yes."
Burundi, facing its worst crisis since an ethnically charged civil war ended in 2005, is high on the agenda for the two-day summit as violence that has killed hundreds of people rattles a region where memories of Rwanda's 1994 genocide are still raw.
Officials have said African leaders would try to persuade President Pierre Nkurunziza - who triggered the crisis by standing for a disputed third term in July elections - to accept such a force. They also said they were unlikely to succeed.
"When it comes to troops, our position has not changed. It is a no-go area under any conditions," Burundi's Foreign Minister Alain Nyamitwe told reporters in Addis Ababa.
Leaders from the 15 members of the council met on Friday in a bid to resolve differences but failed to reach a decision, said Smail Chergui, the AU's peace and security commissioner.
An African diplomat said South Africa and Tanzania, two main brokers of the peace deal that brought Nkurunziza to power in 2005, were among those opposed to sending an unwanted force.
Ivan Simonovic, U.N. assistant secretary-general for human rights, said a failure to deploy troops would be a concern, but the AU should at least send more African human rights observers or send police.
"At the moment, it is important to increase international presence in one or the other form," he told Reuters.