Efforts by Jack Straw, UK foreign secretary, to play down transatlantic tensions over European Union plans to lift an arms embargo on China were called into question on Monday as a senior US official rejected his suggestion that Washington misunderstood the proposal.

The official said the EU was underestimating the strength of feeling in Washington over arms sales to Beijing. “A failure to understand the significance of this issue is going to result in major problems for transatlantic arms procurement,” he warned.