Updated

The United Nations is formally ending its support for a Congo military offensive against a rebel group after two Congolese generals linked to human rights violations were picked to lead the operation.

The U.N. had been looking forward to a move against the FDLR militant group, which was formed by extremist Rwandan Hutus who fled into eastern Congo after taking part in the 1994 Rwanda genocide. The top U.N. envoy to Congo, Martin Kobler, has said the end of the FDLR will be "a turning point which will fundamentally alter the security situation" in the region, where several armed groups have competed for control of vast mineral resources.

A U.N. official on Friday said letters are being sent this weekend to Congolese authorities about the cessation of support. The official spoke on condition of anonymity because of the sensitivity of the issue.

The United Nations has repeatedly warned Congo in recent days over Gen. Bruno Mundevu and Gen. Fall Sikabwe, saying they are known to be heavily involved in "massive human rights violations" and should be replaced before the U.N. supports the offensive.

A U.N. spokesman, Farhan Haq, last week said talks were under way "at the highest level" with Congo's government over the issue.

Congo's lack of a response to the U.N.'s pressure follows another move by President Joseph Kabila to take an independent path on the offensive.

After a deadline passed in early January for the estimated 2,000 FDLR rebels to turn themselves in, the U.N. pressed publicly for joint military action. But Kabila then declared that his forces would lead the operation, supported by the U.N. peacekeeping force in Congo.

An email to Congo's mission to the U.N. requesting comment Friday evening did not bring a response.

It remains unclear whether the Congolese military offensive has actually begun. Its challenges include picking out the rebels, who are experienced guerrilla fighters and can easily blend into the population. Civilians fear they will be caught in crossfire.

The U.N., whose 19,500 troops in Congo make up the world body's largest peacekeeping force, has said it continues to support other Congolese military operations. Its support for the offensive against the FDLR would resume if the two generals are removed.