The U.S. is ramping up its efforts to put pressure on Iran’s Islamic regime, thought to be pursuing a nuclear weapons program, by squeezing the country’s oil sector. Late Thursday night, the U.S. State Department announced sanctions against three large oil companies—including, including, in a bold move, China’s Zhuhai Zhenrong—for selling refined oil products to Iran. “This is an extremely unfriendly signal,” said analyst Li Guofu of the China Institute for International Studies, speaking with the Financial Times. Refined oil products are considered crucial to Iran’s economy since the country doesn’t have the domestic infrastructure to refine crude oil on its own. The targeted sanctions come as Treasury Secretary Tim Geithner visited Asia’s two largest economies this week, pressuring China and Japan to reduce the amount of oil they import from Iran. Japan, which imports 10 per cent of its oil from Iran, pledged to reduce its crude trade with Iran after Geithner’s visit.