Joining a chorus of concerns over the pace of exit negotiations from companies like Airbus and BMW, Dassault CEO Eric Trappier said aerospace companies needed more clarity on the break-up.

"They want in a certain way to divorce. The question after the divorce, are you still friends? The answer I think is yes. Are you still countries in geographic Europe? The answer is yes," Trappier said.

"The only question now is what are going to be the new agreements of the future. We should in a very short time start discussion about a new agreement between the UK and the EU".

Trappier issued the appeal on behalf of French and European aerospace companies in an interview with Reuters at the Farnborough Airshow this week.

Airbus has warned that production could be affected if Britain leaves the EU with no decision on issues such as whether to remain in the European Aviation Safety Agency.

British Prime Minister Theresa May told aerospace officials this week her negotiating plan would be good for jobs in the sector.

"We need to understand and to know about the rules and we would like these rules to be as light as possible compared to what we had before," Trappier said.

Trappier heads the French aerospace industry association, GIFAS, and European lobbying group ASD, which represents the European aerospace, defence and space sectors in Brussels.

Trappier took a sanguine view about growing trade and political tensions between the United States and Europe, such as U.S. President Donald Trump's description of the EU this week as a "foe," but called for a stronger Europe to defend its interests.

"I think we need to be careful about what is said and what is a reality. As far as GIFAS is concerned and I am concerned we don't see the United States as an enemy. We see them as a big partner," he said.

"Obviously when you are speaking about a partner it has to be based on a certain balance; it can't be the strong and the weak. ... I may say also it is time for Europe to organize itself to be strong... If you are a strong EU speaking with a strong U.S. then I think balance is going to be back."

(Reporting by Tim Hepher; Editing by Susan Fenton)