Bulgaria has been seeking diversification of energy sources and routes for supply. This was stated at a meeting in Sofia between Minister of Energy Temenuzhka Petkova and EU ambassadors. The minister pointed out work on the gas interconnector with Greece, which will be operational by 2020. The power lines between Bulgaria and Romania, Bulgaria and Greece, and Bulgaria and Serbia, allow for at least 15% interconnection. Minister Petkova added that Bulgaria relied on coal-fired power stations to work until 2030-2050. These plants can be used with local raw energy sources, sufficient for another 60 years. The power plants provide 60% of electricity during the winter and significant amounts of money have been invested in sulfur cleaning systems. Ambassadors expressed a keen interest in the Belene NPP project and the gas drilling projects in the Black Sea.