U.S. Secretary of State John Kerry called on Britain on Tuesday to maintain the closest possible links with the European Union as it negotiates to leave the bloc, saying the unity of Europe was paramount for transatlantic relations.

 

Speaking in Brussels, Kerry sought to make the case for the European Union despite the rise of anti-EU populist parties and Britain's vote to exit. He said there could be no place for isolationist policies.

 

"We will not be shy about where our interests lie: We need the strongest possible EU, the strongest possible UK and a highly integrated, collaborative relationship between them," Kerry said in a speech.

 

"We should never take for granted the good achieved by the unity of Europe," he said, adding that "some people do so too quickly," recalling his youth as the son of a U.S. diplomat growing up in divided Berlin in the 1950s.

 

Britons' decision to leave the 28-member bloc on June 23dealt a huge blow to the European project of greater unity, and alarmed Washington which feared that the post-war stability it helped to underpin was at risk.

 

The departure of Washington's closest ally in the bloc comes as the European Union and the United States are negotiating a trade pact that could encompass almost half the world's economy.

 

Anti-EU political parties, who are placing unprecedented pressure on the center-left and center-right establishment in Europe, have seized on the proposed pact as a sign of unbridled capitalism, saying it will lower standards and benefit only multinational companies.

 

While Kerry said that the West needed to move on from the British referendum result, he criticized European politicians who he said failed to promote the benefits of the European Union over the past six decades.

 

Echoing an intervention by President Barack Obama last April in London in support of the EU, the world's biggest trading bloc, Kerry said the continent's post-war recovery and its ensuing prosperity was "one of the greatest stories in the history of human kind".

 

In what appeared to be a direct appeal to Euroskeptics, he also questioned, in an age of free-trade, technological connectivity and the complex threats facing the West, how any country could break away from the international order. "Who could credibly argue that each nation, operating in a vacuum, would somehow be more efficient and effective?"