(Adds context, quotes) MOSCOW, June 28 (Reuters) - Russian billionaire Vladimir Potanin, majority shareholder in mining giant Norilsk Nickel (Nornickel), said on Monday the impact of new duties on the company was expected to be around $500 million, the RIA news agency reported. Russia has introduced temporary new export taxes for steel products, nickel, aluminium and copper which will cost producers $2.3 billion between Aug. 1 and Dec. 31. Potanin also said he was in ongoing talks with Nornickel’s second-largest shareholder, Rusal, about the fate of their shareholder agreement, which expires in early 2023. The agreement covers matters such as dividend policy. The parties’ approaches continue to differ, but “there is no tension”, he said. The shareholders will work out a new long-term dividend formula before the agreement expires, he said. “A formula that would be valid for five years would be sensible,” Potanin was cited by the Interfax news agency as saying. “I assume that by the time the agreement is finalised, such a formula will have been worked out, and we will be able to give such additional comfort to investors.” (Reporting by Anastasia Lyrchikova Writing by Polina Ivanova Editing by Jan Harvey and Mark Potter) Our Standards: The Thomson Reuters Trust Principles.