A military junta in Guinea said its transition back to civilian rule will probably take more than three years, a proposal likely to upset West Africa's political bloc that has called for a swift return to constitutional order after last year's coup.

Colonel Mamady Doumbouya, the head of the junta that took power in September, told state television late on Saturday that after political consultations he was considering a transition of 39 months, the first time he has proposed a timeline.

Military leaders have snatched power in Mali, Burkina Faso and Guinea over the last two years, raising concerns of a backslide in democracy in West Africa that over the past decade had begun to shed its reputation as a "coup belt".

The coups have put the countries at odds with the region's main political and economic bloc, the Economic Community of West African States (ECOWAS), which is trying to put power back in civilians hands.

ECOWAS has already imposed broad sanctions on Mali after military leaders proposed holding onto power until 2025, hammering its fragile economy by shutting it off from regional trade and financial markets. ECOWAS has given Mali 12-16 months to arrange democratic elections.

When Burkina Faso's leaders proposed a 3-year transition to civilian rule, ECOWAS called for "a more acceptable timeline" but stopped short of imposing sanctions on the impoverished state.

ECOWAS has imposed sanctions on Guinea's junta leaders but not on the wider economy. A spokesperson was not available for comment on Guinea's new timeline.

(Reporting by Saliou Samb; Writing by Edward McAllister Editing by Alexandra Hudson)