The first contingent of West African peace troops is due to arrive in coup-stricken Guinea-Bissau later Sunday, a security official said.

"The first group from the ECOWAS (Economic Community of West African States) force is expected to arrive tonight," an intelligence official told AFP on condition of anonymity.

The 15-state regional bloc on Thursday decided to send troops to stabilise the troubled nation following a coup on April 12, between the two rounds of a presidential election in which outgoing prime minister Carlos Gomes Junior was the frontrunner and the opposition claimed fraud.

At a summit in Abidjan, ECOWAS gave Guinea-Bissau's junta 72 hours to agree to a return to constitutional order and to allow in 500 to 600 troops or face targeted sanctions.

The intelligence official did not specify the number or nationality of the troops making up the advance party expected on the ground Sunday.

Nigeria, Togo, Ivory Coast and Senegal are expected to contribute to the force. Its deployment is also aimed at facilitating the withdrawal of a 650-strong Angolan force, whose presence is one of the junta's grievances.

News of the ECOWAS force's imminent deployment came as the Bissau-Guinean crisis' military and civilian players were gathered in Banjul for talks, together with seven of the region's foreign ministers.

"We have nothing against the people of Guinea Bissau; ECOWAS is here to help you solve your problem but I can also assure you that ECOWAS' patience is running out," Gambian President Yahya Jammeh said.

"In less than seven years, how many presidents in Guinea lost their lives? How many chiefs of staff lost their lives? How many people have been killed with impunity, here you have to make a choice.

"We are here to tell you that as a last resort, for you to choose between a peaceful resolution with ECOWAS and yourselves or ECOWAS will take measures to put an end to what is happening in Bissau," Jammeh said.