The US Treasury said it had "serious concerns" about the value of the renminbi,the Financial Times reported. While not openly accusing China of manipulating its currency, the Obama administration has toughened its stance. Recent moves to accumulate more foreign exchange reserves "risk unwinding some of the progress made in reducing imbalances," the Treasury said in its semi-annual report on exchange-rate policies. While the administration has made efforts rebalance the relationship between the US and China within the multilateral framework of the G20, US labor groups and legislators argue that the undervalued renminbi makes China’s exports unfairly cheap. If the US officially labels China a "currency manipulator," China would be subject to trade sanctions, adding to tensions after the recent introduction of US tariffs on Chinese tire imports.