Mr. Wen's forthright comments reflect a new dynamic in what is arguably the most important bilateral relationship in the world. As the only major economy still growing strongly, and the U.S.'s largest creditor, China is behaving with new assertiveness. Beijing has emerged from the global recession with a fresh confidence about its state-led economy, which has delivered stimulus projects from high- speed railways to highways and bridges with remarkable efficiency. At the same time, it makes no secret of its disdain for U.S. economic management, and is in no mood to be lectured by Washington about how to support the world economy.