France says Macron and Johnson will try to de-escalate post-Brexit fishing row

French President Emmanuel Macron and British Prime Minister Boris Johnson agreed on Sunday to try to de-escalate a row over post-Brexit fishing rights, a French official said after days of threats raised the prospect of new trade barriers.

The leaders, who have given conflicting signals over whether they wanted to turn down the heat in the dispute, used a private meeting on the sidelines of a Group of 20 leaders' summit in Rome to try to ease tensions.

The French official said Macron told Britain it should obey the rules which Paris accuses London of flouting by failing to give France enough fishing licences to operate in British waters.

Britain says it is meeting the conditions of the post-Brexit trade agreement.

"The goal for both the president and the prime minister was to work towards de-escalation," the official told reporters after a one-on-one meeting between the two leaders.

"We are giving ourselves the space for de-escalation in the coming hours."

Britain stepped up a war of words with France on Saturday, with Johnson refusing to rule out triggering trade dispute action and his Brexit minister sharply criticising a suggestion by Paris that the EU should show that there was "more damage to leaving the EU than to remaining there". 

Relations with France have become increasingly strained since Britain voted to leave the EU in 2016 with London's recently struck security pact with the United States and Australia doing little to build trust with Paris.

Macron has questioned Britain's "credibility". 

Paris has said it might impose targeted measures on British ships and goods from Tuesday, including increasing some checks if the fishing dispute is not resolved.

The French official said Macron told Johnson he expected mutual respect and the two sides would have "exchanges" over the coming hours to work out ways to de-escalate the situation.

"We'll see on Nov 2. We're not there yet. One thing at a time," the official said.