Washington has informed Beijing that it is "very concerned" about the new energy deal agreed by state-owned oil giant Sinopec to develop Iran's Yadavaran oil and gas field, the Financial Times reported. The deal, which was signed on December 9 and has been valued by Iran's oil minister at US$2 billion, suggests a rift may be emerging between China and the US over dealing with Tehran and its nuclear program. Investments in Iran's energy sector are not banned under the terms of UN sanctions but they are seen as a potentially useful point of leverage in negotiations with the country. Washington is likely to ask the UN Security Council to approve another round of targeted sanctions to try and force Iran to end its uranium enrichment program. To do this, it would need the support of both China and Russia.