After Boris Johnson's election win last month, U.S. President Donald Trump said Britain and the United States were now free to strike a "massive" new trade deal after Brexit, which Trump said could be "more lucrative" than any EU deal.

But in an interview with Reuters in Paris, French trade minister Jean-Baptiste Lemoyne said a mid-sized power like Britain will find it tough to negotiate alone with the world's biggest economy.

"I've seen the statements boasting about a great trade deal with the United States," Lemoyne said.

"But I think the British will come to realise how different it is to negotiate as part of a bloc like the European Union, which has 500 million consumers, than as a country of 60 million or so. The power dynamic is not the same."

Lemoyne also warned European negotiators against rushing into a "botched" deal because of the tight deadline before the end of the transition period at the end of the year, when EU rules stop applying to the United Kingdom.

"We're going to have to work flat out," Lemoyne said. "What's certain is that content must prevail over timing. We can't afford to botch some issues.

"Talks will certainly be tough, but we can't give too much away or be negligent about certain rules that matter to us because there's a tight deadline," he added.

Johnson has set a hard deadline to reach a new trade deal with the EU, betting that the prospect of another Brexit cliff-edge would force Brussels to move more quickly to seal an accord. London also hopes it can get a deal with the United States done before the U.S. presidential election in November.

French President Emmanuel Macron consistently took a hard stance on Brexit during the first phase of negotiations.

At the last EU summit in Brussels, he warned Britain against a deregulation of its economy, saying that would prompt the EU to shut off access to Britain's biggest export market.

But the stakes are high for France, since Britain represents its biggest trade surplus, being a destination for French wines, champagne, cars and drugs. Trade minister Lemoyne said Britain often does not have domestic alternatives, which should help strike a deal.

"We're lucky to have complementarities with Britain. I think these should be encouraged," he said.

(Writing by Michel Rose; additional reporting by Gus Trompiz; Editing by Leigh Thomas and Alex Richardson)

By Michel Rose