MOSCOW (Reuters) - Rosneft does not have enough crude to ship to buyers with which it has long-term supply deals, making it hard for the Russian company to continue with record oil cuts beyond June, four sources familiar with the matter told Reuters on Thursday.Rosneft has told the energy ministry it would be difficult to maintain cuts to the end of the year, as it has had to cut shipments to major buyers, such as Glencore and Trafigura, despite good demand, two sources close to the talks said..