"This morning and today all (were) saddened ... by the news of a horrible attack in Idlib – chemical weapons as the worst of the war crimes - and whoever is responsible for that must be held accountable," Mogherini said in a joint press point with UN Special Envoy for Syria, Staffan de Mistura following a meeting with civil society.

"Impunity is not an option, especially in front of these terrible scenes we are seeing today. And maybe it is not by chance that it is exactly when the international community, 70 different countries and organisations come together to try and build peace, supporting the UN mediation in Geneva, gathering funds for the humanitarian support and looking at the future and how the international community can support the Syrians as they build the future of Syria," she said, referring to Wednesday's Brussels conference, 'Supporting the future of Syria and the region', hosted and co-chaired by the EU.

The conference will look for ways to support the Syrian people to try and find their way to their own future, with humanitarian help, with support for the political negotiations in Geneva and by looking at what the international community can do in the future to reconstruct the country once a political transition is underway. 

With a view to the potential reconstruction of Syria, the EU has started work with the UN and the international financial institutions to prepare for a major collective effort that will be needed when the conflict is over and a political agreement has been reached. 

"No reconstruction will be financed before that," Mogherini stressed. "Obviously all the humanitarian aid and all the humanitarian support will continue to come in. That is a must for us and as you know the European Union is the first humanitarian donor for Syria with almost €10 billion we have mobilised together with our Member States so far. That will continue, that is a priority for us. But the reconstruction effort, the reconstruction financing, will only be starting when the political process will start and an agreement will be reached in Geneva."