Speaking after final negotiations wrapped up, Tusk said the deal become possible because it was "positively assessed by Ireland."

The key change in the new deal is that British PM Boris Johnson agreed to replace the backstop with a four-year regulatory alignment between Northern Ireland and the EU. This was always a major sticking point in negotiations, with British Conservatives an unionists in Northern Ireland opposed to having the region treated differently to the rest of the UK.

Tusk said the new deal ensures the integrity of the single market, avoids chaos and safeguards peace and stability on the island of Ireland.

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