BRUSSELS, March 7 -- Facing the prospect that the US might cut them adrift under President Donald Trump, European Union leaders launched a day of emergency talks on Thursday in a bid to step up their own security and ensure that Ukraine will still be properly protected.

Friedrich Merz, the likely next chancellor of Germany, and summit chairperson Antonio Costa discussed in Brussels ways to fortify Europe's defences on a short deadline.

Merz pushed plans this week to loosen the nation's rules on running up debt to allow for higher defence spending. "Spend, spend, spend on defence and deterrence. That's the most important message," said Danish Prime Minister Mette Frederiksen. The call is a sharp departure from decades of decline in militar...