The shadows of Russia and Brexit loom over a "minefield" summit of European Union leaders in Brussels on Thursday at the end of a tumultuous year for the crisis-hit bloc, comments AFP.

The EU leaders will hold dinner without British Prime Minister Theresa May where they will try to present a united front over how they handle Britain's departure from the bloc.

They are also expected to rollover sanctions against Moscow over the conflict in Ukraine for another six months, but are unlikely to impose any new measures in response to the carnage in Aleppo.

The one-day summit, cut back from the usual two days, wraps up an annus horribilis for the bloc that has seen it face a wave of populism including the shock Brexit referendum vote.

At their 15 December 2016 European Council meeting, EU Leaders will mainly discuss migration, and internal and external security, as well as the issue of Ukraine and Syria. 

The objective is to discuss among the EU-27 the structure and the process of the negotiations to be held once theUnited Kingdom formally notifies its intention to withdraw from the European Union under Article 50 TEU.

The rollover is expected despite little appetite among some countries, and fears that US President-elect Donald Trump is set to take take a much softer line on Moscow amid signs of rapprochement with Vladimir Putin.

The EU leaders are however set to stop short of threatening any new sanctions against Russia over the violence in Syria's Aleppo, where the army has seized nearly all the ravaged city.

The leaders will say in a statement obtained by AFP that the EU "strongly condemns" the assault by the "Syrian regime and its allies, notably Russia" and calls on them to allow aid in to Aleppo.

Britain's May will then leave the summit while the other 27 discuss the process for dealing with Britain's departure once May triggers the two-year divorce process, which she has promised to do by the end of March 2017.

The 27 will also agree that the European Commission will lead the talks, under French chief Brexit negotiator Michel Barnier, but that the European Council of member states must also be involved in the talks.

The EU 27 have refused all negotiations with Britain until the process begins, while warning that May is likely to have only a short window until October 2018 to broker a deal.

Brexit minister David Davis said Wednesday a transitional deal to cover the period after the two years before a full trade agreement is reached was possible "if necessary".