FILE PHOTO: Participants hold a British Union flag and an EU flag during a pro-EU referendum event at Parliament Square in London, Britain June 19, 2016. REUTERS/Neil Hall

BRUSSELS (Reuters) - The 27 European Union countries expect to adopt on Tuesday their negotiating mandate for talks about their relationship with Britain after Brexit, paving the way for the launch of talks as early as next week, a senior EU diplomat said on Monday.

Britain left the EU on Jan. 31 and the two sides have been talking tough in the run-up to a new round of negotiations. The EU is demanding far-reaching guarantees of fair competition and London is saying it will not be bound by the bloc’s rules on the so-called level playing field.

“The expectation is to adopt the negotiating mandate tomorrow, which would allow us to start negotiations very soon, even as early as next week,” the diplomat said.

France had held up agreeing the EU’s joint negotiating stance, seeking to strengthen the level playing field provisions, including to oblige Britain to follow the bloc’s rules and regulations in future in exchange for access to the EU’s cherished single market.

But the 27 national envoys to EU hub Brussels agreed a text on Monday that says any new trade treaty between the EU and Britain “should prevent distortions of trade and unfair competitive advantages so as to ensure a sustainable and long-lasting relationship”.

“The envisaged agreement should uphold common high standards, and corresponding high standards over time with (European) Union standards as reference point,” said the document, which was seen by Reuters.

It covers state aid, competition, social, employment and environmental standards, as well as relevant tax regulations.

European affairs ministers of the 27 are due to rubber stamp the mandate for the bloc’s executive Commission, which negotiates with Britain, on Tuesday.

“We are ready to offer a highly-ambitious trade deal providing that level playing field is ensured, as well as close cooperation in many other areas,” said Croat minister Andreja Metelko Zgombic who will chair the Tuesday session as Zagreb currently holds the EU’s rotating presidency.