European Union foreign and defense ministers will grapple next week over the structure and powers of a new EU diplomatic corps, a foreign service that is expected to end up with 7,000 staff. The External Action Service is being created as part of the Lisbon Treaty, which came into force last year with the aim of simplifying the EU's decision-making and giving the union of 27 countries more clout in world affairs. On paper, having a diplomatic branch to represent the EU and its 500 million citizens abroad may make sense. But it is a challenge to bring the plan to reality quickly while satisfying the vested interests of the EU's institutions and member states. As well as the structure of the service, which will have about 4,500 diplomats abroad and 2,500 in Brussels, Britain's Catherine Ashton, the EU's foreign policy chief, needs to agree with member states on the reach and responsibilities of the corps and secure the European Parliament's budgetary approval. She will discuss these elements with European defence ministers in Luxembourg on Sunday, before foreign and defence ministers hold separate talks on Monday on a range of topics, including the EAS, Afghanistan, Sudan and Somalia. “She's moving ahead rapidly with getting the structure in place, but there's a lot of issues to be resolved and hoops to be jumped through to bring it into being,” said an EU diplomat. Discussions over the detailed structure and responsibilities of the EAS are expected to last several more weeks, with the service unlikely to be officially up and running – with parliamentary backing –until the end of the year. Aside from balancing the various visions that France, Britain, Germany and others may have for the service and how it is staffed, another difficulty Ashton faces is deciding what foreign and security policies to prioritise. The EU is the world's largest trading bloc by value and a close partner of the United States, but it also wants to improve ties with China, India, Brazil, Russia and in Africa, while not ignoring its European neighbours such as Turkey and the Balkans. But it will struggle to do all that at once with a brand new diplomatic corps. So it must put certain relationships above others and emphasise issues that it thinks it can have an impact on, such as development policy or Iran sanctions. Diplomats working for Ashton say she is focused on closer relations with China and India, and will also concentrate on EU ties with Bosnia, Ukraine, Turkey and Somalia, whose security forces the EU is training.