Mongolia plans to start charging interest on allegedly unpaid tax owed by Rio Tinto Group’s Oyu Tolgoi LLC, as talks continue over the future of the $6.6 billion copper and gold mine, the nation’s mining minister said. Mongolia wants Oyu Tolgoi LLC, in which Rio controls 66 percent and the government the rest, to pay interest, even as the two sides disagree on whether the tax payment was made. Oyu Tolgoi said Feb. 5 that it pre-paid $150 million in tax in 2010 and 2011 and was due to receive credit for it last year. Mines Minister Davaajav Gankhuyag said today that the payment was a loan and tax obligations are still outstanding.