US unions are trying to restrict Chinese tyre imports, a move that will force Barack Obama to take a firm free trade or pro- labour position.

As Tim Geithner, US Treasury secretary, visited China and called for greater co-operation in the countries' often fractious relationship, hearings began yesterday in Washington on a case brought by the United Steelworkers union to the International Trade Commission.

The USW claims that a surge in Chinese tyre imports has cost 7,000 US jobs. It wants the president to more than halve the number of imports allowed into the country from 46m last year to 21m. The union is appealing using section 421 of the trade law, which requires the ultimate approval or rejection of the president even if the ITC recommends restrictions.