Good news out of Washington is rare. Last week congressional leaders agreed on a bipartisan bill which, if passed, would for the first time in years give the president “fast-track” authority when negotiating trade deals. The bill would be a boost for the prospects of a huge trade deal, the Trans-Pacific Partnership (TPP), binding America with 11 economies (including Japan but not China) around the Pacific rim. Now, as if on cue, come welcome signals about the TPP itself. As Japan's prime minister, Shinzo Abe, prepared to head to Washington for a much-anticipated trip including an invitation to address a joint session of Congress (see article), he claimed that America and Japan were close to agreement over their bilateral terms―on which the whole TPP deal hinges.

　　Yet there are two big caveats. First, fast track, formally known as Trade Promotion Authority, may still fall foul of Congress. Second, Japan may not make any serious cuts to tariffs that protect its farmers. Those outcomes are more likely because the Obama administration and the Japanese government have made a similar mistake: both have been too quick to cast the TPP as a weapon in the containment of China.

　　Flanked by Japan and America, the TPP would link countries which make up 40% of global GDP. It could boost world output by $220 billion a year by 2025. It is supposed to reform difficult areas such as intellectual property, state-owned firms and environmental and labour standards. It would join economies―from Vietnam to Australia―that lie at different ends of the spectrum of development.

　　But the TPP will not happen without fast track, which forces Congress into a yes/no vote on any pending trade deal and so avoids the risk that it will be amended into oblivion. And the passage of fast track faces a lot of scepticism from Democrats (see article). Some are implacably opposed. Others want America to have a bigger arsenal with which to fight against unfair traders. Driven by a conviction that China artificially holds its currency down and destroys American jobs, Charles Schumer, a powerful senator from New York, is determined that fast track should include a provision that would make sure a trade deal included sanctions on currency manipulation.

　　Attaching a currency-manipulation clause to trade deals is a poor idea, both because the practice is hard to define and because the addition of such clauses makes reaching an agreement less likely. But since the Obama administration has pitched TPP as a counterbalance to an assertive China, Mr Schumer's demands are harder to ignore.

　　The same mistaken logic looks set to cause problems in Japan. Mr Abe committed his country to joining the TPP on strategic grounds―as a counterweight to China―rather than because he is a born admirer of free trade. When he entered negotiations, some of his backers thought that, by playing the China card, Japan would be spared from making real concessions: that America would care more about a pact that excluded China than about prising open Japan's most protected markets, particularly rice. Even now, Japan seems to want to keep tariffs high. The best it may offer is to allow in a fixed quota of tariff-free rice from the TPP's other members, America included.

　　If the China-containment logic leads to a minimalist agreement, then the economic gains from TPP will be slim. TPP's real value is to set high new standards for world trade, and that demands the boldest possible agreement. And in the long run the world gains most if China joins. The rhetoric makes trade negotiations sound like a contest. In fact, it is a battle where the more you give away the more you win.