The party of the ousted president Alpha Conde and opposition groups that had opposed him united in denouncing the decision.

Their statements came as UN chief Antonio Guterres called on the military junta in Burkina Faso, Guinea and Mali to hand power back to civilians as soon as possible.

Junta leader Colonel Mamady Doumbouya made his announcement in a speech broadcast on television Saturday, saying the National Transition Council (CNT) would put the proposal to parliament.

A day earlier, the army-dominated government had said the forum considering the issue had considered a transition period of between 18 and 52 months. Doumbouya said the period he had opted for was the "median proposal".

But the influential FNDC coalition, which includes some 20 political groups, said in a statement that choice had no legal basis and was "inadmissible, inconceivable and unacceptable".

It added: "The attitude of the authorities... constitutes a threat to peace and national unity."

The FNDC, which staged huge protests against Conde before he was overthrown, also argued it ignored widespread calls for an inclusive dialogue under the supervision of the international community.

Conde's former party the Rally of the People of Guinea (RPG) also rejected the decision. It too called for an inclusive dialogue under the mediation of the international community to fix a "consensual" calendar.

Doumbouya said Saturday his decision had been reached after an inclusive consultation process, but it was boycotted by several prominent political groups who disputed its legitimacy.

Guterres made his comments Sunday after talks in Dakar with Senegalese President Macky Sall.

They had agreed on the need to keep talking to the de facto authorities in all three countries so as to get a swift return to "constitutional order", he said.

- Regional pressure -

The 39-month delay proposed by Doumbouya also goes against the timetable set out by regional players such as the West African bloc ECOWAS, raising the possibility of further sanctions against the regime.

In September 2021, army officers led by Colonel Mamady Doumbouya ousted elected president Alpha Conde in the impoverished former French colony.

Conde, 84, had drawn fierce opposition after he pushed through a new constitution in 2020 that allowed him to run for a third presidential term.

Following the coup, ECOWAS called for a return to civilian rule within six months.

Although many Guineans initially welcomed the coup, there is growing discontent against the junta in the nation of 13 million people.

Guinea's coup last September came on the heels of a military takeover in Mali.

ECOWAS has applied sanctions on members of the Mali junta, shut its borders with the country, frozen its assets at the Central Bank of West African States and imposed a trade embargo.

For Guinea, leading junta members have been sanctioned and are subject to a travel ban within the bloc.

A third ECOWAS member, Burkina Faso, experienced a coup in January.

It has so far escaped the sanctions handed out to Guinea and Mali but is standing by a three-year schedule for holding elections, arguing that it first has to deal with a bloody jihadist insurgency.