By Elizabeth Piper and Gabriela Baczynska
LONDON/BRUSSELS (Reuters) - Prime Minister Theresa May will outline on Thursday her approach to the "hugely important issue" of reassuring EU expatriates about their futures in Britain, at a summit that is her first Brexit test since an election sapped her authority.
Over coffee at the end of dinner on the first day of the EU summit, May will address the other 27 leaders and describe "principles" of her plan to give early guarantees to some three million people living in Britain who come from other countries in the bloc.
But her wings have been clipped - not only in Britain where voters denied her a majority in parliament, but also in Brussels where EU leaders will try to stop her from discussing Brexit beyond a quick presentation.
Instead, once she has left the room, they will continue their own discussion of Britain's departure from the European Union.
"My understanding all along is that this is a hugely important issue for Britain and for the 27 that has been clear from the very outset of this process," a senior British government source said of the question of EU expatriates.
"We want to provide early assurance, and it has always been our position that we want to outline our principles at this dinner and that is what we are going to do."
The source said Britain was "perfectly content" with the arrangements. Last week, one diplomat said May had tried to "hijack" the summit taking place on Thursday and Friday by drawing other leaders into wider discussions on Brexit. [nL8N1JD4VX]
Another British official said May would offer "new elements" in a paper to be published early next week. There may be sticking points with Brussels, such as the cut-off date for EU citizens in Britain to retain rights under the bloc's free movement rules.
To show the "goodwill" her aides often refer to, May will have a separate conversation with European Council President Donald Tusk and hopes to have other one-on-one meetings. But it is not clear whether she will make any headway on the Brexit talks, which began in Brussels on Monday.
Weakened by an election she did not need to call, May has watered down her government's program to try to get it through parliament and set a softer tone in her approach to Brexit.
Yet her aims have held - she wants a clean break from the bloc, leaving the lucrative single market and customs union and so reducing immigration into Britain and removing her country from the jurisdiction of EU courts.
On Monday, her Brexit minister, David Davis, described the first day of Brexit talks to unravel more than 40 years of union as setting a "solid foundation" for future discussions. [nL8N1JG16K]
But one Western diplomat from a non-EU country said it was hard to see how some members would be open to fruitful discussions.
"Some are still grieving, some are mad and some are just sad," the diplomat said. "They seem to spend more time complaining about what Britain says rather than cracking on with a deal that will produce a strong Britain and strong EU."
A senior EU diplomat said the bloc was ready to listen to what May had to say.
"The EU 27 position is clear in terms of what conditions we'd like to see for our citizens there and what we can offer for UK citizens here," the diplomat said.
May will also aim to show that while still a member of the EU, Britain will contribute to other summit discussions, pressing for more action to encourage social media companies to clamp down on internet extremism and for the EU to roll over sanctions against Russia over the Ukraine crisis.
She will announce a new 75 million-pound ($95 million) package of aid for migrants and help for them to return to their home countries, in the hope of discouraging people from making the "treacherous journey" to Europe.
(Additional reporting by Alastair Macdonald, Robin Emmott, Jan Strupczewski, Elizabeth Miles and Alissa de Carbonnel in Brussels; editing by Andrew Roche)