Rwanda - along with Argentina, Australia, Luxembourg and South Korea - was elected in October as a temporary member of the 15-nation UN Security Council for 2013-14.
Analysts say the new group will likely be more friendly to the West on crises like Syria or North Korea but lacks the power to force an end to the impasses on those issues.
The Security Council's "Group of Experts" has accused Rwanda and Uganda of backing so-called M23 rebels in eastern Democratic Republic of the Congo in their fight against the Congolese army. Uganda and Rwanda deny the group's allegations.
"Our role (on Congo) will be positive as it has always been," Olivier Nduhungirehe, Rwanda's deputy UN ambassador, told Reuters. "We will continue supporting the peaceful resolution of the conflict."
"We will also support (UN Secretary-General Ban Ki-moon's) efforts in bringing together leaders of the region, in order to address the root causes of the conflict," he said.
But he made clear Kigali would not tolerate any further finger pointing regarding what he said were unfounded charges.
"Rwanda will not be part of and will not support any attempt to continue the blame game initiated by a politicised and discredited Group of Experts," Nduhungirehe said.
Security Council diplomats have told Reuters on condition of anonymity that they worry it will be more difficult to achieve consensus on Congo with Rwanda on the council. At the same time, they said, any solution for eastern Congo must include Rwanda, so having it on the council is not necessarily a bad thing.
Diplomats say that Rwanda's leverage is its influence over M23.
The last time Rwanda was on the council was in 1994-95. That coincided with a genocide in which 800 000 people were killed when Rwanda's Hutu-led government and ethnic militias went on a 100-day killing spree, massacring Tutsis and moderate Hutus.
The council's new composition will not break the deadlocks on Syria or North Korea, council diplomats say. The Security Council has been at an impasse on Syria since that conflict began 21 months ago, with veto powers Russia and the United States unable to agree on whether Syrian President Bashar Assad should be required to step down or not.
In addition to India and South Africa, Colombia, Germany and Portugal are leaving the Security Council. Azerbaijan, Guatemala, Pakistan, Togo and Morocco will remain through 2013.