London - The head of the World Trade Organization (WTO) says it would not be "the end of the world" if Britain failed to reach a post-Brexit trade deal with the EU, but there would be costs.
Roberto Azevedo told the Sunday Telegraph newspaper that although Britain would be better off with an agreement, the impact of falling back on WTO rules would be "manageable".
"About half of the UK's trade is already on WTO terms -- with the US, China and several large emerging nations where the EU doesn't have trade agreements," he said.
"So it's not the end of the world if the UK trades under WTO rules with the EU."
Britain intends to leave the EU's single market and customs union when it withdraws from the bloc in March 2019, but hopes to reach a free trade agreement (FTA) with Brussels before then.
However, trade talks have yet to formally start, and without a deal, bilateral trade would likely be subject to higher WTO tariffs as well as other barriers such as increased red tape.
"If you don't have a fully functioning FTA with the EU, there could be rigidities and costs -- but it's not like trade between the UK and EU is going to stop," Azevedo said.
"There will be an impact, but I suppose it is perfectly manageable."
Ahead of Britain's EU referendum in June 2016, Azevedo warned that exporters risked billions of pounds (dollars, euros) in extra customs duties each year after Brexit.
In a speech in London, he noted that Britain's EU membership gave it preferential trading terms not only with the other 27 member states, but also the 58 countries with which the bloc had FTAs.
Britain is currently seeking to replicate the EU's trade deals with third countries, although it cannot sign any agreements until after Brexit.
EU leaders are meeting next month to discuss whether to start trade talks with Britain, but are demanding commitments on a financial settlement and the Irish border issue.
International Trade Secretary Liam Fox told Sky News on Sunday: "Of course we would rather get a deal with the European Union but we're not afraid not to get a deal."