An employee views the Port of Shanghai from an office window, January 19, 2011. REUTERS/Carlos Barria

BRUSSELS (Reuters) - China has raised concerns about European Union plans to negotiate an ambitious free trade deal with the United States, fearing it is a protectionist move, a senior EU official said on Tuesday.

Chinese officials queried EU foreign policy chief Catherine Ashton about the issue when she visited Beijing at the end of April for talks with Foreign Minister Wang Yi and other Chinese leaders.

The 27-nation EU and the United States aim to launch negotiations on a transatlantic free trade deal by the end of June, with discussions set to last at least two years.

China worried about whether the plan was “a pulling of the wagons into a circle to ... insulate the transatlantic economy from the rest of the world or is it, as we argue, even greater opening of both economies?” the EU official said, briefing journalists on condition he was not further identified.

The EU argues that a deal would strongly benefit the United States and the EU but other countries would also profit from the expansion of trade and investment across the Atlantic.

“That was the reassurance we gave to the Chinese,” the official said.

The European Union is China’s biggest trading partner.

Chinese officials raised the possibility of Beijing negotiating its own free trade agreement with the EU, a prospect that the EU official did not rule out “in the medium to longer term.”

A transatlantic trade deal could add 0.5 and 0.4 percent respectively to European and U.S. gross domestic product, according to a European Commission report, although it could take a decade to deliver those effects.