European Union leaders met Sunday to approve a historic Brexit deal, with one declaring Britain's withdrawal a "tragedy", but holding out hope of close future ties.
Arriving for a special summit in Brussels, European Commission President Jean-Claude Juncker, head of the bloc's executive arm, said it was a "sad day".
"To see a country like Great Britain... leave the EU is not a moment of joy nor of celebration, it's a sad moment and it's a tragedy," he said.
Michel Barnier, the former French foreign minister who negotiated the deal on behalf of the bloc, added: "We will remain allies, partners and friends."
"No victors here today, nobody winning, we're all losing -- but given that context, this (agreement) is acceptable."
Lithuania president Dalia Grybauskaite said as she arrived: "We will endorse the Brexit agreement, but there is nothing good for any side because it is withdrawal from the EU."