By Tom Miles

GENEVA (Reuters) - Britain needs to sort out its relationship with the European Union before it can begin to talk to the United States about any post-Brexit trade deal, U.S. Trade Representative Michael Froman said in Geneva on Monday.

"The practicality is that until the UK sorts through with the EU the nature of its relationship ... it’s impossible to have a serious conversation about knowing what kind of trade agreement you can have with the UK separately," Froman said.

"Is it part of the customs union or not? Is it part of the single market or not? What areas does it have sovereignty over? Does it have sovereignty over tariffs? Does it have sovereignty over regulation?"

Such questions needed to be the priority for Britain, Froman told an audience of academics and trade diplomats at Geneva's Graduate Institute.

"Until those sorts of questions are further clarified, it's hard to have a serious conversation about what the nature of what a future U.S.-UK trade relationship might look like."

He declined to offer any advice for Britain's trade minister, Liam Fox, saying he spoke to Fox and his colleagues periodically and "my sense is they are getting quite enough advice as it is."

He also declined to comment on the possible impact on U.S. trade relationships if Donald Trump wins the U.S. presidential election next month.

(Reporting by Tom Miles; Editing by Larry King)