EU's Tusk says Johnson letter offered no 'realistic alternatives' to Brexit backstop

European Council President Donald Tusk said on Tuesday that a letter sent to him by British Prime Minister Boris Johnson included no "realistic alternatives" to the contentious Irish backstop.

"The backstop is an insurance to avoid a hard border on the island of Ireland unless and until an alternative is found," Tusk said in a Tweet, responding to a Johnson letter on Monday proposing that the European Union agrees to drop the backstop.

"Those against the backstop and not proposing realistic alternatives in fact support re-establishing a border. Even if they do not admit it."