US deputy secretary of state Robert Zoellick has said the April 11 deadline set by the US and the EU to resolve a dispute over state aid to rival aircraft makers Boeing and Airbus is unlikely to be met.

In October, the US lodged a complaint against EU subsidies to Airbus with the World Trade Organisation, which brought a counteraction from the EU against what it termed indirect US government aid for Boeing through defence and research contracts.

On Jan 11, the two sides gave themselves 90 days to negotiate the phasing out of such subsidies, in a bid to avoid a dispute.

But Mr Zoellick, who used to be the US trade representative, said: "From my last conversation with European Trade commissioner Peter Mandelson, I do not see that as probably reaching the fulfilment in the time that we set forth.

On March 21, Mandelson had said: "The ball is in America's court".

Tension between the two sides has risen sharply, with each blaming the other for an abrupt end to a telephone call between Mandelson and Zoellick.