Transatlantic rifts are set to feature prominently when Trump arrives at the G7 summit in France to discuss differences over trade, Iran and climate change.

The EU said last month it would retaliate with extra duties on 35 billion euros' worth of US goods if Washington imposes punitive tariffs on EU cars.

The Sino-US trade war has also spurred fears of a broader global economic slump.

"We see trade tensions as the single most important risk factor to the growth of the global economy," the senior EU official said. The bloc would be seeking to defuse them and to concentrate on a "positive" EU-US trade agenda.

Since the EU's chief executive, Jean-Claude Juncker travelled to Washington for trade talks with Trump a year ago, the bloc's imports of US liquefied natural gas have tripled, while those of soybeans have doubled, according to the official.

"We can continue on that pathway where we also have an opportunity for both the US and the EU to reach a deal on the elimination of industrial tariffs," the official said. If such an agreement is reached, the EU estimates that each side will generate an additional 26 billion dollars or euros in exports.

The EU would also prefer to resolve a dispute between aircraft manufacturers Boeing and Airbus without resorting to tariffs, the official said.

Separately, a Trump administration official told Reuters that Washington could agree a trade declaration in the French resort town of Biarritz with new British prime minister Boris Johnson, who will also be there and is making overtures to the US president as Brexit looms.

"It wouldn't be an agreement on any trade issues. But it would be a statement about how to proceed, what the roadmap might be, what they were looking for from the trade negotiators and economic ministers," the senior White House official said.

Speaking on condition of anonymity, the official said that any such statement would signal determination on the part of the United States to support Britain through the Brexit process.

While Brexit marks an unprecedented rollback of European integration and has been a shock to the EU, Trump has praised it as an opportunity and offered warm words on Johnson himself, highlighting another fundamental disagreement straining the partnership between Washington and Europe.