Feingold, who took over as Great Lakes envoy in September, met DRC President Joseph Kabila on Tuesday before flying to Kigali where he was expected to meet President Paul Kagame.
Last week the UN stepped up pressure on the DRC government and the M23 to reach agreement at long-running negotiations in Kampala.
This weekend Feingold was among foreign observers in the Ugandan capital and, along with Martin Kobler, the head of the UN intervention force Monusco, stayed until late on Sunday night to push for progress in the negotiations.
Since the 1994 Rwandan genocide Washington has had close ties to the English-speaking leadership in Kigali.
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But the M23 rebellion, when members of a former rebel group who had been integrated into the DRC army mutinied, complaining that a previous agreement, signed on 23 March 2009, had not been implemented, opened a division between the US and Rwanda.
Rights groups, including US-based Human Rights Watch, have accused the M23 of numerous atrocities against civilians and their leaders have been accused of exploiting the mineral resources of North Kivu, a region of DRC that borders on Rwanda.
A UN report accused the Rwandan army of recruiting for th rebels and giving them logistical support, alsp claiming that highly placed Rwandans actively supported the movement.
For the last two years the US has suspended military aid to Kigali over the question.
US Secretary of State John Kerry phoned Kagame last weekend and Feingold has shuttled back and forth in the region over the last couple of weeks.
"We have the impression of having someone we can talk to, who understands our concerns," a member of the DRC delegation to the Kampala talks told RFI's Sonia Rolley, while the Rwandans "appreciate" that he is pressing Monusco to combat other armed groups, including the Rwandan Democratic Liberation Forces, in the area.
Feingold is also reported to be opposed to an amnesty for M23 leaders accused of war crimes and the rebels' reintegration into the DRC army, both positions that Kinshasa defended during the talks.
"Feingold without doubt has the most balanced position possible, given his aim - end the repeated rebellions and foreign interference in Congo," a diplomat stationed in the region told RFI.