By Justyna Pawlak and Parisa Hafezi GENEVA (Reuters) - Big powers resumed talks on Wednesday on a preliminary deal to curb Iran's nuclear program with Russia and Britain confident a breakthrough could be clinched and Iran spelling out "red lines" but saying it wanted friendly ties with all nations. Keen to end a long standoff and head off the risk of a wider Middle East war, the United States, Russia, China, France, Britain and Germany came close to winning concessions from Tehran on its nuclear activity in return for some sanctions relief at negotiations in Geneva earlier this month. Russian Foreign Minister Sergei Lavrov said earlier: "We hope the efforts that are being made will be crowned with success at the meeting that opens today in Geneva." Chinese Deputy Foreign Minister Li Baodong, head of China's delegation in Geneva, told Reuters: "Things are on track." Western governments suspect Iran has enriched uranium with the covert aim of developing the means to fuel nuclear weapons, which Tehran denies.