Opec+ nations are close to finalizing a “charter” for a long-term alliance, with a document likely to be signed as soon as this week, said two delegates.

Members of the group received a revised draft of the document on Sunday that appeared to have broad support, one of the delegates said, asking not to be named because the information was private. There were only a few final details of the charter to resolve, another delegate said.

Since the Organization of Petroleum Exporting Countries joined forces in 2016 with non-members including Russia, Kazakhstan and Mexico, they have sought to establish an enduring basis for cooperation beyond the current production-cuts agreement. While the group appears set to extend those supply curbs into 2020, previous attempts to finalize the draft charter have faltered.

A year ago, Opec+ was considering setting up a permanent body with its own constitution and secretariat, potentially marking a seismic shift in oil’s world order and create a rival organization to Opec. By November, those plans had faded as Russian Energy Minister Alexander Novak said there was no need to create a new “bureaucratic apparatus.”

Still, the Russian minister, who alongside his Saudi counterpart Khalid Al-Falih dominates decision making in the group, has continued to support a formal underpinning for their cooperation. He said in February that “legal and technical points“ of a long-term charter were being finalized.

The biggest question is whether the charter would have the support of Iran, which has voiced unhappiness with the dominance that Russia and Saudi Arabia exert on Opec+ policy. Bijan Namdar Zanganeh, the Iranian oil minister, is scheduled to arrive in Vienna for talks with fellow members on Monday morning.

The final elements of the charter now in focus include how the entity will be financed, and whether Opec nations would sign the document individually or as one bloc, said a delegate.