European Union leaders agreed on Thursday to open formal membership negotiations with Ukraine and Moldova, despite an earlier threat from Hungary to veto the deal.

A European diplomatic source told AFP that Hungarian Prime Minister Viktor Orban had agreed not to be in the room when the other 26 leaders backed a consensus decision.

European Council President Charles Michel, host of the EU summit, announced the agreement in a social media post, dubbing it: "A clear signal of hope for their people and for our continent."

A senior European official told reporters: "There has been a decision of the European Council on this matter which has not been opposed by any member of the European Council."