BRUSSELS (AP) — British Prime Minister Theresa May's show of goodwill at the European Union summit left the 27 other EU leaders with "thousands of questions" and eagerly awaiting a more detailed proposal on the future right of EU citizens to remain in a departed Britain.

Even if some leaders applauded May's commitment to treat EU citizens seeking to remain in Britain beyond 2019 with the utmost respect, others remained wary that her words would not necessarily be reflected in the legal position of Britain's negotiating team, which should be presented to Parliament on Monday.

"I want to reassure all those EU citizens who are in the U.K., who've made their lives and homes in the U.K., that no one will have to leave, we won't be seeing families split apart. This is a fair and serious offer," May said as she entered Friday's final day of the EU summit.

Many leaders were nonplussed by the move, saying there was a clear deal to leave such issues to the top negotiators, Michel Barnier for the EU and David Davis for Britain.

"There are thousands of questions to ask," said Dutch Prime Minister Mark Rutte after May laid out her proposals to the leaders during a dinner. In a separate session without the British leader, the others pondered the meaning of it all.

"We told each other when she was gone 'OK, this is interesting but now it must go to Michel Barnier'," Rutte said.

"We don't want to buy a pig in a poke," said Belgian Prime Minister Charles Michel, calling May's opening "an extremely vague proposal for something which is incredibly complicated."

German Chancellor Angela Merkel too insisted that a huge number of issues remained open, though she welcomed May's first hint of a negotiating stand as "a good start."

May promised that EU citizens will not be immediately kicked out of Britain when it leaves the union and says their fate will be a priority in Brexit negotiations.

May laid out benchmarks for the rights of 3 million EU citizens living legally in Britain and how they should be shielded from excessive harm because of the divorce. She made it clear that Britain wants reciprocal measures for the 1.5 million British citizens living in the EU. The issue of citizens' rights is especially sensitive in the Brexit talks.

Under May's proposal, EU citizens with legal residence in the U.K. will not be asked to leave and will be offered a chance to regularize their situation after Brexit. May also promised to cut the burdensome bureaucracy such paperwork can involve. EU citizens had faced an imposing 85-page form to fill in to stay if they wanted to stay.