By Camillus Eboh, Boureima Balima and Felix Onuah
ABUJA/NIAMEY (Reuters) -West African defence chiefs have drawn up a plan for military action if Niger's coup is not overturned by Sunday, the regional bloc said on Friday, after mediation failed in a crisis that threatens regional security and has drawn in global powers.
The Economic Community of West African States (ECOWAS) has given Niger's coup leaders until Sunday to step down and reinstate elected President Mohamed Bazoum.
The bloc has taken a hard stance on last week's takeover, the seventh coup in West and Central Africa since 2020.
Given its uranium and oil riches and pivotal role in the war with Islamist rebels in the Sahel region, Niger has strategic significance for the United States, China, Europe and Russia.
The United States government has paused certain foreign assistance programs that benefit the government of Niger but will continue giving humanitarian and food assistance, U.S. Secretary of State Antony Blinken said on Friday.
Under the intervention plan, the decision of when and where to strike will be made by heads of states and will not be divulged to the coup plotters, Abdel-Fatau Musah, ECOWAS commissioner for political affairs, peace and security, said.
"All the elements that will go into any eventual intervention have been worked out here, including the resources needed, the how and when we are going deploy the force," he said at the close of a three-day meeting in Nigeria's capital Abuja.
Whatever option the 15-nation body chooses risks further conflict in one of the poorest regions of the world where groups linked to Islamic State and al Qaeda thrive on chaos.
It is not clear how much support the bloc has. Neighbouring Chad, which is not a part of ECOWAS but whose military leader, President Mahamat Idriss Deby, played a role in mediation efforts this week, said it would not intervene militarily.
"We always advocate dialogue between Nigeriens and we will never intervene by military means," Chad's defence minister, General Daoud Yaya Brahim, told national television on Friday.
ECOWAS has already imposed sanctions on Niger and sent a delegation to its capital Niamey on Thursday seeking an "amicable resolution". But a source in the entourage said that they were rebuffed and did not stay long.
"We want diplomacy to work, and we want this message clearly transmitted to them that we are giving them every opportunity to reverse what they have done," Musah said.
Nigerian President Bola Tinubu told his government to prepare for options including deployment of military personnel, in a letter read out to the Senate on Friday. Senegal has also said it would send troops.
The junta has denounced outside interference and said it would fight back.
The 59-year-old coup leader, Abdourahamane Tiani, served as battalion commander for ECOWAS forces during conflicts in Ivory Coast in 2003, so he knows what such intervention missions involve.
Support for him from fellow juntas in neighbouring Mali and Burkina Faso could also undermine the regional response. Both countries have said they would come to Niger's defence.
Detained at the presidential residence in Niamey, Bazoum, 63, who was elected in 2021, said in his first remarks since the coup that he was a hostage and in need of U.S. and international help.
"If it (the coup) succeeds, it will have devastating consequences for our country, our region and the entire world," he wrote in a Washington Post opinion piece, backing ECOWAS' economic and travel sanctions.
The junta has cited persistent insecurity as its main justification for seizing power, but data on attacks shows security had actually been improving, while violence has soared since juntas took control in Mali and Burkina Faso.
Like the leaders of those countries, Niger's junta revoked military cooperation pacts with former colonial power France.
France has between 1,000-1,500 troops in Niger, supported by drones and warplanes, helping battle groups linked to al Qaeda and Islamic State. The United States, Germany and Italy also have troops stationed in Niger.
Paris shrugged off the decision, saying on Friday that though it had seen the statement by "some Nigerien army men", it only recognised legitimate authorities.
Niger has also withdrawn its troops operating in northern Nigeria under a regional military joint task force that is fighting Islamist insurgents in the Lake Chad region, two army sources from Niger and Nigeria said on Friday.
The sources, who are not authorised to speak to the media, said Niger troops had completed their withdrawal on Thursday night.
Western donors have cut support in protest, even though Niger relies on aid for 40% of its budget. Regional countries have imposed economic sanctions that residents said were starting to bite.
Bazoum said the coup spelt chaos for his nation, with prices already soaring, and Islamists plus Russia's private mercenary group, Wagner, likely to exploit the situation.
"With an open invitation from the coup plotters and their regional allies, the entire central Sahel region could fall to Russian influence via the Wagner Group, whose brutal terrorism has been on full display in Ukraine," he wrote.
Yevgeny Prigozhin, the head of Wagner which has forces in Mali and the Central African Republic, last week said his forces were available to restore order in Niger.
Russia on Friday repeated its call for a return to constitutional rule.
Some Nigerien supporters of the coup waved Russian flags and denounced France and ECOWAS in a protest march on Thursday.
(Reporting by Boureima Balima and Moussa Aksar in Niamey and Felix Onuah and Camillus Eboh in Abuja; Additional reporting by Andrew Osborn in Moscow, Kanishka Singh in Washington, Heine Friederike in Berlin and Michel Rose in Paris; Writing by Emelia Sithole-Matarise, Nellie Peyton and Edward McAllister; Editing by Andrew Cawthorne, Cynthia Osterman, Andrew Heavens, Alistair Bell and Sandra Maler)