The world’s largest oil producers are pressing ahead with talks for an unprecedented deal to mitigate the devastating impact of the coronavirus crisis on their industry, even as their leaders exchange barbs. The challenge now is to nail down numbers everyone can live with. Ministers and diplomats will spend the next two days talking about who’s willing to cut production, and by how much. The most important contributions will come from oil’s trio of big powers: Saudi Arabia, Russia and the U.S.

An effective deal will require all three to participate, but not every barrel cut will be the same. Russia and Saudi Arabia are set to curb their production significantly, said people familiar with the negotiations. The U.S. is more likely to offer up the kind of gradual output reductions that will come as American companies respond to a market where prices are low and storage tanks are full. “They’re already cutting back and they’re cutting back very seriously,” U.S. President Donald Trump said of U.S. oil producers at a briefing in Washington on Monday. “I think it’s happening automatically.”

After a turbulent few days in which Trump’s prediction of a historic output cut was followed by sniping between Moscow and Riyadh, there were signs that diplomats were making progress. U.S. Energy Secretary Dan Brouillette held a “productive discussion” over the phone with his Saudi counterpart Prince Abdulaziz bin Salman, the U.S. government said.