Prime Minister David Cameron is to propose curbing the benefits European Union migrants can claim in negotiations with EU president Donald Tusk ahead of a referendum on whether Britain should leave the bloc.
Under Cameron's proposal, an "emergency brake" to in-work benefits would come into force immediately after the referendum, due to be held by 2017.
"What form an emergency brake takes is set to be the main issue at tonight's dinner in Downing St after the EU institutions backed down last week and conceded that EU nationals should have to pay into the UK welfare system before receiving benefits," a senior government source said.
"A deal will only be possible if a brake would apply to current levels of EU migration to Britain, could be triggered immediately after the referendum and would apply long enough to resolve the underlying problem."
The working dinner comes with Tusk expected to publish draft proposals early this week on how to reform Britain's relationship with the EU, which Cameron can then use to campaign against a so-called "Brexit".
Cameron is under increasing pressure from his own centre-right Conservative party, which has a strong eurosceptic contingent, to come back with a robust deal.
Opinion polls currently suggest that Britons would vote to leave the EU by a small margin.
British officials hope that a final deal can be nailed down at a Brussels summit being held on February 18 and 19.
That could then open the door to a referendum in June.
But Cameron insists he is willing to hold out for as long as it takes to secure the right package of reforms, if necessary delaying the referendum until September or even next year.
Cameron has set out four areas in which he wants reform -- migrant benefits, safeguards against more political integration in the EU, protection of countries such as Britain which do not use the euro currency and boosting economic competitiveness.
The main sticking point has been Cameron's insistence that EU migrants employed in Britain must wait four years before claiming certain welfare payments, which could require a treaty change.
"The Prime Minister intends to leave Tusk in no doubt that he will not do a deal at any price," added the source.
Tusk's visit comes after Cameron held a hastily-arranged meeting with European Commission chief Jean-Claude Juncker on Friday to try to resolve the British leader's main concern -- reducing the number of EU migrants coming to Britain.
Cameron emerged from the talks with Juncker saying that, while there had been "progress", the proposal on the table was "not good enough".
