Officials from Rwanda and the Democratic Republic of Congo have reached a draft agreement aimed at ending decades of conflict.

The breakthrough, mediated by the US and Qatar, provides for the "disengagement, disarmament and conditional integration" of armed groups fighting in eastern DR Congo.

Rwanda denies widespread accusations that it backs one of those groups, the M23, which has seized large parts of the region this year.

It also includes provisions for a joint security mechanism to prevent future flare-ups. The peace deal is expected to be formally signed next week.

The deal could open the way for billions of dollars of western investment in the mineral-rich region, which been plagued by conflict for three decades.

However, analysts say that many questions still remain about the contents of the peace deal.

The US State Department said technical teams had initialled the draft text on Wednesday, ahead of a formal signing ceremony next Friday to be witnessed by US Secretary of State Marco Rubio.

In a statement, it said the deal was reached during three days of "constructive dialogue regarding political, security, and economic interests" between officials of the two countries in Washington.

The latest draft agreement builds on a previous accord signed earlier, it added.

In late April, Rwanda and DR Congo signed an agreement in Washington, promising to respect each other's sovereignty and come up with a draft peace deal within days.

The decades-long conflict escalated earlier this year when M23 rebels seized swathes of mineral-rich territory in eastern DR Congo.

Rwanda denies supporting the M23, insisting its military presence in the region is a defensive measure against threats posed by armed groups like the FDLR - a rebel group composed largely of ethnic Hutus linked to the 1994 Rwandan genocide.

Rwanda in turn accuses the Congolese government of backing the FDLR, which is denied by DR Congo.

The M23 captured Goma in late January, followed by the city of Bukavu, and has since set up governing structures in the regions under its control.

Thousands of people have been killed and hundreds of thousands of civilians forced from their homes in recent months following the rebel offensive.

The questions which are yet to be answered in the draft agreement include:

• Will the M23 rebel group withdraw from areas they have occupied?
• Does "respect for territorial integrity" mean Rwanda admits having troops in eastern DR Congo and will withdraw them?
• Would the agreed "return of refugees" allow thousands of Congolese back from Rwanda?
• Does "disarmament" mean that the M23 will now lay down their arms?
• Who will disarm the FDLR, after the failure of several previous attempts?
• Would the agreed humanitarian access allow the reopening of the Goma airport for aid supply?

Following the loss of territory, the government in Kinshasa turned to the US for help, reportedly offering access to critical minerals. Eastern DR Congo is rich in coltan and other resources vital to global electronics industries.

Peace deals between the two countries have unravelled in the past.

Last year, Rwandan and Congolese experts reached an agreement twice under Angolan mediation on the withdrawal of Rwandan troops and joint operations against FDLR - but ministers from both countries failed to endorse the deal. Angola eventually stepped down as a mediator in March.

Additional reporting from Emery Makumeno in Kinshasa