Former Polish prime minister Donald Tusk has won a second term as European council president, overcoming bitter opposition from Poland that has left the country isolated in Europe.
His reappointment until the end of 2019 means he will play a crucial role in Britain's negotiations to leave the EU.
Poland refused to approve some summit texts, raising unease at a time when the E.U. is looking for unity as the crisis-prone bloc is faced with the painful departure of Britain.
"I will do my best to make EU better," Tusk said in a tweet.
The leaders voted 27 to one to give him another two-and-a-half-year term.
The Polish Government insisted that Tusk had violated his mandate by interfering in domestic politics.
According to the Guardian, Polish Prime Minister, Beata Szydlo, confirmed that Poland would retaliate by blocking the EU summit communique, a statement summarising EU policy on economic growth, migration and the western Balkans. But the document can still be approved in a different procedure, a manoeuvre likely to deepen the wedge between Warsaw and other EU capitals.