However, the United Nations denies it has any direct contact with Ntaganda, who is wanted by the International Criminal Court but joined the DRC army in January.
The UN says Congo has assured it that he is not playing a significant role in the operations.
“We just feel that anybody who has committed war crimes should not participate in military operations of this sort at the moment and he needs to be held accountable,” Howard Wolpe, Washington’s envoy to the Great Lakes, said.
He told a news conference there were “serious concerns” about the impact on civilians of the operations against the Democratic Forces for the Liberation of Rwanda (FDLR) rebels.
“We’re trying now to work with (MONUC) and others to manage that situation in a way that will allow continued pressure on the FDLR but hopefully minimise the risk to civilians,” he said.
The United Nations said earlier this month that it was committed to continuing to support Congo’s army and that it had only withdrawn assistance from certain units it believes killed more than 60 civilians in recent fighting.
Great lakes “neglected”
Dynamics have changed sharply in eastern Congo this year, with traditional foes Congo and Rwanda launching joint operations. But human rights experts have rounded on the United Nations for not challenging Ntaganda’s new role.
Ntaganda led the armed wing of the Tutsi-dominated National Congress for the Defence of the People (CNDP) guerrilla group before signing up to a peace deal at the start of this year. He is wanted by ICC prosecutors for recruiting child soldiers.
In May, UN experts said they had a document and testimonies from senior army commanders and sources close to the CNDP former rebellion confirming Ntaganda was deputy commander, despite another officer being officially named.
The joint attacks on the Rwandan Hutu FDLR rebels, some of whom took part in Rwanda’s 1994 genocide and have since been at the heart of much of Congo’s violence, have helped improve DRC-Rwanda relations and ended the once powerful CNDP rebellion.
Congo’s 1998-2003 war sucked in a half dozen of the vast nation’s neighbours and triggered a humanitarian disaster that has killed an estimated 5.4 million people over the past decade. Despite the conflict’s official end, much of the east remains a volatile patchwork of rebel fiefdoms and militia strongholds.
Wolpe said his appointment was a sign of the Obama administration’s intent to re-engage with the troubled region.
“There was this feeling that for many years now there has been an absence of coordination and an absence of energy behind the diplomatic effort,” he said.
“Certain parts of the continent have been neglected.”