FILE PHOTO: United States Ambassador to the United Nations Mike Waltz speaks during a meeting at U.N. headquarters in New York City, U.S., September 23, 2025. REUTERS/Shannon Stapleton/File Photo

By Michelle Nichols

UNITED NATIONS, Dec 12 (Reuters) - The United States accused Rwanda on Friday of fueling instability and war as a Rwanda-backed advance of the M23 rebel group in eastern Democratic Republic of Congo threatens to derail U.S. President Donald Trump's efforts to broker peace in the region.

“Rwanda is leading the region towards increased instability and war,” U.S. Ambassador to the U.N. Mike Waltz told the U.N. Security Council. “We will use the tools at our disposal to hold to account spoilers to peace.”

The rebels' gains bring the conflict to the doorstep of neighboring Burundi, which has had troops in eastern Congo for years, aggravating fears of further regional spillover of fighting that has already killed thousands of people and displaced hundreds of thousands more since January.

'RESTRAINT HAS ITS LIMITS': BURUNDI

"Let me be clear: restraint has its limits. Should these irresponsible attacks continue, it would become extremely difficult to avoid a direct escalation between our two countries," Burundi's U.N. Ambassador Zephyrin Maniratanga told the Security Council.

Rwanda's U.N. Ambassador Martin Ngoga accused Burundi of an attack on Rwandan territory and said: "Rwanda is not waging war against the Republic of Burundi and has no intention of doing that." He accused DRC of violating the ceasefire and said Rwanda was fully committed to implementing its part of the Washington peace deal.

Congo's Foreign Minister Therese Kayikwamba Wagner called on the Security Council to hold Rwanda accountable.

“We have reached a moment of truth - either the international order accepts being openly defied, namely by Rwanda, or this council assumes its responsibility. Impunity has gone on for far too long,” she told the council.

ADVANCE FOLLOWS LEADERS MEETING WITH TRUMP

M23 says it is fighting to protect ethnic Tutsi communities in eastern Congo. The latest M23 advance in mineral-rich eastern Congo comes a week after Congolese President Felix Tshisekedi and his Rwandan counterpart Paul Kagame met Trump in Washington and affirmed their commitment to a U.S.-brokered peace deal.

"We call on Rwanda to uphold its commitments and to further recognize the government of the Democratic Republic of Congo's right to defend its territory and its sovereign right to invite Burundian forces onto its territory," Waltz told the 15-member council. "We are engaging with all sides to urge restraint and to avoid further escalation, including refraining from hostile anti-Tutsi rhetoric."

"The United States is profoundly concerned and incredibly disappointed with the renewed outbreak of violence in the eastern DRC," Waltz said.

He told the Security Council that Rwanda has had strategic control of M23 and what he referred to as the rebel group's political wing - the Congo River Alliance, or AFC - since it re-emerged in 2021.

"Kigali has been intimately involved in planning and executing the war in eastern DRC, providing military and political direction to M23 forces and AFC for years now," Waltz said. "The Rwandan defense forces have provided materiel, logistics and training support to M23, as well as fighting alongside M23 in DRC with roughly 5,000 to 7,000 troops as of early December."

Rwanda denies backing M23 and has blamed Congolese and Burundian forces for the renewed fighting.

M23 is not party to the Washington-mediated negotiations. It has been participating in a separate, parallel round of talks with the Congolese government, hosted by Qatar.

(Reporting by Michelle Nichols; Editing by Katharine Jackson, Rod Nickel)