WASHINGTON — Secretary of State Marco Rubio on Friday oversaw the signing by Congo and Rwanda of a pledge to work toward a peace deal that would ease U.S. access to critical minerals in resource-rich eastern Congo, bringing U.S. influence to bear in a minerals trade that has helped fuel conflict that has killed millions for three decades.

Rubio’s participation in the Washington ceremony with his Central African counterparts is an early step in what the Trump administration says is a rebuilding of U.S. foreign policy to focus on transactions of direct financial or strategic benefit to the United States.

Congo and Rwanda hope the involvement of the United States — and the incentive of major investment if there’s enough security for U.S. companies to work safely in east Congo — will calm the fighting and militia violence that have defied peacekeeping and negotiation since the mid-1990s.

The risk is that the United States becomes involved in or worsens the militia violence, corruption, exploitation and rights abuses surrounding the mining and trade of east Congo’s riches.

“A durable peace ... will open the door for greater U.S. and broader Western investment, which will bring about economic opportunities and prosperity,” Rubio said, adding that it would “advance President Trump’s prosperity agenda for the world.”

Congo is the world’s largest producer of cobalt, a mineral used to make lithium-ion batteries for electric vehicles and smartphones. It also has substantial gold, diamond and copper reserves.

Congolese President Felix Tshisekedi has sought out a deal with the Trump administration that could offer the U.S. better access to his country’s resources in exchange for U.S. help calming hostilities.

Eastern Congo has been in and out of crisis for decades with more than 100 armed groups, most of which are vying for territory in the mining region near the border with Rwanda.

The conflict has created one of the world’s largest humanitarian disasters with more than 7 million people displaced, including 100,000 who fled homes this year.

Conflict in eastern Congo is estimated to have killed 6 million people since the mid-1990s, in the wake of the Rwanda genocide. Some of the ethnic Hutu extremists responsible for the 1994 killing of an estimated 1 million of Rwanda’s minority ethnic Tutsis and Hutu moderates later fled across the border into eastern Congo, fueling the proxy fighting between rival militias aligned to the two governments.

“Today marks not an end but a beginning,” Congolese Foreign Minister Therese Kayikwamba Wagner said Friday before signing the broad agreement, which commits Rwanda and Congo to draft a peace accord and work to instill security and a good business environment, allow the return of the millions of displaced and accomplish other goals.

“The good news is there is hope for peace,” she said. “The real news is peace must be earned.”

She directed part of her remarks to the civilians of east Congo, brutalized, isolated and displaced by the fighting: “We know you are watching this moment with concern, with hope and, yes, with doubt. You are entitled to actions that measure up to the suffering you have endured.”