Angolan President Joao Lourenco "is working to bring the two leaders together to take action on the roadmap that we and regional leaders have outlined," Molly Phee, the top US diplomat for Africa, told a congressional hearing.
Angola, a growing partner of the United States, has led diplomacy aimed at ending years of instability in the DRC.
Phee said the United States had a "commitment to trying to reduce the tragedy" in the eastern DRC, where a May 3 attack on a camp for displaced people killed 35, according to DRC officials.
In March, Angola said that Rwandan President Paul Kagame and DRC President Felix Tshisekedi had agreed in principle to meet.
But relations have since deteriorated after the camp attack.
The United States said that Rwandan armed forces were involved in the attack alongside the mostly Tutsi M23 rebels fighting in DRC's east, and has demanded that Kigali hold people accountable.
Rwanda has rejected the US accusation as "ridiculous." In turn, Kigali has demanded that the DRC crack down on Hutu militants linked to the 1994 genocide in Rwanda, which mostly targeted Tutsis.
Phee, questioned by a lawmaker, said the United States was pressing both sides.
Washington wants the DRC to act in "addressing the genocidaires that threaten Rwanda and on Rwanda's side ceasing its military engagement in eastern DRC and its support for the M23 group which is conducting atrocities," she said.
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