BRUSSELS (Reuters) - An EU official said on Wednesday that the European council president, Donald Tusk, is likely to tell British Prime Minister David Cameron that the EU offer to freeze in-work benefits for migrants could unravel if other countries demand the same.
Tusk will travel to London on Thursday for a donor conference on Syria and will meet Cameron separately to take stock of reactions to the EU proposal.
Cameron is negotiating new terms for Britain's membership in the European Union prior to a national referendum on whether the country should leave the bloc.
"One of the messages that I expect Tusk will send to Cameron is that in social benefits the risk comes not only from the concerns of central European countries about their workers in Britain, but also from countries that are maybe in a similar situation as Britain, that are also receiving workers from other EU countries, that might be tempted to seek similar solutions," the EU official said.
"It would unravel the British deal, really, because the basic assumption is that this is a proposal for the UK," the official said.
The EU offered to allow Britain to freeze in-work benefits for migrant EU workers - notably from Poland - for up to four years in recognition of the large number who have come to Britain over a long period.
The deal also linked child benefits to living costs in the country where the worker's children reside, which means smaller pay-outs for workers from Eastern Europe.
The deal has yet to be approved by all 28 governments of the EU and is far from sealed, officials said.
"The child benefit is different, it is for everybody," the EU official said. "When it comes to the in-work benefits, it is quite clear that the deal talks about a significant inflow over an extended period of time, which the UK has experienced,"
Tusk is also scheduled to meet at the same London conference with German Chancellor Angela Merkel and other European leaders.
Reporting By Jan Strupczewski; Editing by Angus MacSwan