CHINESE officials like to lecture their American counterparts that, when it comes to loosening their tightly controlled currency, pressure is counterproductive. Tim Geithner, the treasury secretary, has resisted direct confrontation with China over the yuan's value. Like his predecessors, he worries that overt pressure would undermine advocates of reform inside China, principally the People's Bank of China, and erode co-operation on other issues such as Iran and North Korea.

When China said in June that the yuan would be allowed more flexibility, it looked like a victory for Mr Geithner. But as weeks elapsed and the yuan stayed put, the critics began to resurface. “We're all coming to the conclusion that they don't believe we're serious,” Jack Reed, a Democratic senator, told Mr Geithner on September 16th. “And as a result, they will listen to you politely but they will not take any effective action.”

The administration increasingly appears to agree. On September 15th it brought two actions against China at the World Trade Organisation (WTO): one contesting Chinese duties on American exports of a special type of steel used in power generation, and another over discrimination against foreign providers of payment-card transactions. The previous week the United Steelworkers union asked the administration to sue China in the WTO over subsidies of its renewable-energy industry. America has previously ignored such “Section 301” petitions or settled them bilaterally. But Mr Obama may not hold to that pattern, given his ties to unions and a deadline to respond that falls just before the mid-term elections (extensions can be granted).

The government's most potent lever, however, is Congress, where numerous bills aimed at punishing China are in the works. The most important is a bipartisan bill pushed by Tim Ryan and Tim Murphy, Democratic and Republican congressmen respectively, that would subject imports benefiting from an undervalued currency to countervailing or anti-dumping duties. The House of Representatives could vote on the bill as early as next week; Senate prospects are less certain. Mr Geithner has been surprisingly open to the proposal, provided it complies with WTO rules (many experts believe it does not). This is a change from the reactions, ranging from ambivalence to hostility, that similar bills have elicited from the White House in the past.

The tougher tone seems to be working. The yuan began rising earlier this month, though it has not yet matched its progress in 2005, the last time China loosened its grip (see chart). America is not likely to ease off. Having at last got China's attention, it is loth to let it go.