Rwanda's main ethnic Hutu rebel group has announced an end to its armed struggle, after talks in Rome.
Some Hutu rebels have already returned from DR Congo
The FDLR includes members of the Interahamwe, blamed for the 1994 genocide, in which some 800,000 Rwandan Tutsis and moderate Hutus were killed.
They were part of the mass exodus of Hutus who fled into eastern Democratic Republic of Congo after the killings.
The BBC's Rob Walker in Rwanda says the move is a crucial step toward peace in a region plagued by ethnic violence.
The FDLR, which is thought to have about 10,000 fighters, denounced the genocide for the first time and said they would return home and form a political party after receiving safety guarantees.
"We vow to abandon armed struggle and turn to a political process," said Ignace Murwanashyaka of the Democratic Forces for the Liberation of Rwanda (FDLR).
The announcement came after several days of talks in Rome with Congolese government representatives organised by the Sant'Egidio religious community.
The FDLR is one of a number of rebel groups accused of creating instability in eastern DR Congo, where the United Nations is trying to establish security after years of war.
Under a 2002 peace deal to end five years of war in DR Congo, the Hutu rebel groups were supposed to be disarmed but progress has been slow.
UN peacekeepers are disarming militias in eastern DR Congo
The BBC's reporter says the key test will be whether all FDLR commanders in DR Congo do now disarm and return peacefully to Rwanda.
The UN's peacekeeping mission in DR Congo, Monuc, has welcomed the announcement.
"It opens the way to the settlement of the problem of the presence of Rwandan Hutu rebels in [eastern DRCongo]," Monuc spokesman Kemal Saiki told the AFP news agency.
A spokesman for the Rwandan government said his country was ready to receive them, but he said no conditions could be attached to their return.
Rwanda has said that any rebels who participated in the genocide must face justice.
The presence of the Hutu militia has been a constant source of tension between the Rwandan and Congolese governments.
Rwanda has twice invaded its larger neighbour, saying it was doing so to hunt down the rebels.
The last invasion in 1998 sparked a wider war, which sucked in six neighbouring countries and led to the deaths of an estimated 3m people.