The United States has granted exemptions from tough, new sanctions on Iran’s oil trade to seven more economies, leaving China the last remaining major importer exposed to possible penalties at the end of the month.Washington gave waivers to India, South Korea, Turkey and four other countries in return for significantly cutting their purchases of Iranian oil, Secretary of State Hillary Clinton said on Monday.China, which alone buys as much as a fifth of Iran’s crude exports, and Singapore, where much of the country’s fuel oil is blended, did not receive such waivers, ramping up pressure on two important US trade partners in Asia.The sanctions, which the United States may impose starting on June 28, are Washington’s most aggressive measures yet to force Iran to reveal its nuclear programme.The United States and the European Union believe Iran is trying to enrich enough uranium to build a nuclear weapon, while Tehran says the programme is strictly for civilian purposes, primarily to create medical isotopes for use in procedures such as x-rays.Beyond the 27-country EU, which has banned Iranian imports from July under separate sanctions, other buyers of Iran’s crude have pledged to cut purchases by up to a fifth."By reducing Iran’s oil sales, we are sending a decisive message to Iran’s leaders: until they take concrete actions to satisfy the concerns of the international community, they will continue to face increasing isolation and pressure,” Clinton said in a statement.She is hosting talks with ministers from India and South Korea, Iran’s second- and fourth-largest oil buyers, this week in Washington.Geng Shuang, a spokesman for the Chinese embassy in Washington, said his government "opposes unilateral sanctions imposed by one country on others”. He added that China will push for a diplomatic solution to the Iran nuclear issue through negotiations.