By John Irish and Yara Bayoumy

PARIS/WASHINGTON (Reuters) – The United States must step up its support for a planned African force to fight Islamist militants in West Africa otherwise it could fail, leaving French troops to carry the burden alone, France’s defense minister said on Friday.

France intervened in Mali to ward off an offensive by Islamist militants that began in 2012 and 4,000 of its troops remain in the region as part of Operation Barkhane where they work alongside 10,000 U.N. peacekeepers in Mali.

France and West African countries are pushing for the creation of a regional force known as the G5 Sahel.

Washington provides bilateral assistance, intelligence and training for regional security operations, but it is cool toward the African force and has pushed back against U.N. support for it.

“In the Sahel, France is deploying in a high-intensity environment, with tremendous support from the United States. We are immensely grateful for that support,” Parly said in a speech at a Washington think tank monitored in Paris.

“But much more needs to be done. We can’t be, and don’t want to be, the praetorian (guards) of sovereign African countries. They must be made able to defeat terror on their own,” she said during a visit for meetings with her American counterpart James Mattis and White House National Security Adviser H.R. McMaster.

“I would be happy if you could help spread the word in the Beltway,” she said in a reference to the U.S. government.

Parly said the G5 Sahel force was meant to bolster the security capacity of Chad, Niger, Burkina Faso, Mali and Mauritania, which are all former French colonies.

French officials see the success of the G5 Sahel as a long-term exit strategy for Paris. For decades, France has mounted military operations in its former African colonies but in recent years it has looked to spread the cost.

Until now the G5 force has only received a quarter of its estimated 423 million euro budget, according to a report by the U.N. Secretary General, who said financing the operation would “remain a significant challenge” for several years.

“It will start its first operations soon. It needs support. The U.N. wants to give support. I hope everyone can become convinced that a robust U.N. assistance is necessary,” Parly said.

French defense officials say they expect the first G5 patrols to begin this month and hope that will provide momentum ahead of a donor conference in December.

Parly said that militants could flourish if financial backing for the G5 was not forthcoming.

Her visit also aimed to ascertain the political fallout from an ambush in Niger in early October that saw four U.S. special forces soldiers killed by jihadists.

U.S. troops called in French fighter jets for air support and French helicopters to evacuate several wounded soldiers.

(Editing by Matthew Mpoke Bigg)