By Stephanie Kelly NEW YORK (Reuters) -The United States is starting to see success with discussions of a Russian oil price cap by the Group of Seven (G7), as Washington has heard countries are negotiating deals with Russia to buy oil far below the benchmark Brent crude price, a top U.S. Treasury official said Wednesday. U.S. Deputy Treasury Secretary Wally Adeyemo said Russia is trying to lock in contracts ahead of a Dec. 5 European Union ban on seaborne shipments of Russian oil. He did not cite a specific dollar-per-barrel figure on where Russian crude is being sold, though that oil already …