French officials head to Niger on Friday to redefine the country's strategy to fight Islamist militants in the Sahel as thousands of troops complete a withdrawal from Mali and concerns mount over the growing threat to coastal West African states.

Coups in Mali, Chad and Burkina Faso have weakened France's alliances in its former colonies, emboldened jihadists who control large swathes of desert and scrubland, and opened the door to greater Russian influence.

Concerns have grown that the exit of 2,400 French troops from Mali - the epicentre of violence in the Sahel region and strongholds of both al Qaeda and Islamic State affiliates - is worsening violence, destabilising neighbours and spurring migration.

With the withdrawal expected to be completed by the end of the summer, France's new Foreign Minister Catherine Colonna and Defence Minister Sebastien Lecornu arrive in Niger on Friday to seal a regional redeployment.

Niger will become the hub for French troops, with some 1 000 soldiers based in the capital Niamey with fighter jets, drones and helicopters. Some 300 to 400 would be dispatched for special operations with Niger troops in the border regions with Burkina and Mali, French officials told reporters in a briefing.

Another 700 to 1 000 would be based in Chad with an undisclosed number of special forces operating elsewhere in the region. French troops will no longer carry out missions or pursue militants into Mali once the exit is complete, the officials said.

"Beyond Mali, the democratic decline in West Africa is extremely worrying with successive putsches in Mali twice, in Guinea in September 2021, in Burkina Faso in January of this year. France will nevertheless continue despite these events, this withdrawal from Mali, to help West African armies fight against terrorist groups," Colonna told a parliamentary hearing on Tuesday.

"We are currently consulting with our concerned partners to define with them, according to their requests and their needs, the nature of the support that we can provide them."

A French diplomatic source said the aim was to present a new strategy to President Emmanuel Macron in September.

French officials said the onus going forward would be on regional countries to lead on security, while also focusing more on development, good governance and education. The ministers would announce 50-million euro aid to enhance the electricity network in Niger as well as budgetary support.

A key area of concern is how and whether French and European troops will used to support countries in the coastal Gulf of Guinea nations such Benin, Togo and Ivory Coast, where there has been a rise in attacks. Al Qaeda's regional arm has said it would turn its attention to the region.

French officials said that at this stage there had been no formal request for further military assistance. Some European countries had shown an interest in continuing regional operations post Mali, the officials said.

Lecornu will travel to Ivory Coast, which also hosts French troops, on Saturday, while Macron is likely to travel to Benin at the end of July, Colonna said.