Wrenching the United Kingdom out of the EU without a deal means there would be no arrangements to cover everything from post-Brexit pet passports to the trade arteries that pump capital, food and car parts between the two neighbours.
Many investors say a 'no-deal' Brexit would send shock waves through the world economy, hurt the economies of Britain and the EU, roil financial markets and weaken London’s position as the pre-eminent international financial centre.
With such a gulf between the British government and the other 27 members of the EU - whose economy combined is worth $15.9 trillion - some diplomats said Johnson was using international diplomacy for domestic politics.
Some fear that Johnson is setting up a confrontation with the EU that will allow him to reap domestic political capital from what he will cast as EU intransigence.
"Spinning gold from straw has never yet worked. That is also true of Brexit," said Germany's Europe minister, Michael Roth. "Peace in Northern Ireland and the integrity of the internal market are non-negotiable for the EU."
Johnson wrote a four-page letter to European Council President Donald Tusk on Monday asking the EU to axe the Irish border "backstop". EU leaders in Brussels and the other 27 member states issued a swift and unanimous rejection.
