Dozens of people were killed last year in fighting between Bemba's forces and those loyal to Joseph Kabila, who was inaugurated as president in December.
Kabila has told Bemba to slash his personal security detail, which runs to thousands of armed men, to 12 police officers.
Last week, his personal guards were expected to register at an army base where they were to begin their integration into the Congolese security force.
But Bemba's supporters ignored the deadline, saying that under a UN-brokered deal signed last year, he has the right to "an appropriate personal guard".
The Associated Press reported a spokesman as saying Bemba's security was still uncertain.
William Swing, the head of the UN peacekeeping mission to Congo, met Bemba and Antoine Gizenga, the Congolese prime minister, on Wednesday and had been due to meet Kabila on Thursday to try to defuse the situation.
Reuters reported a Western diplomat as saying: "There is a lot still going on behind the scenes ... Both sides are very, very stubborn. I don't see where a breakthrough will come from."