EU President Donald Tusk is due Tuesday to present a proposal responding to British reform demands, with measures including a "red card" scheme to block legislation out of Brussels, according to a government source in London.
British Prime Minister David Cameron is seeking a series of changes to the country's relationship with the European Union before putting its continued membership in the bloc to a referendum.
Following several days of top-level diplomacy, Tusk said Monday that enough progress had been made for him to table a proposal responding to Cameron's demands.
This must then be negotiated with the bloc's other 27 member states, who have so far not been involved in the discussions. The issue is expected to be discussed by EU leaders at their next summit, on February 18-19.
Several of Cameron's demands - which focus on competitiveness, sovereignty, social security and economic governance - face tough resistance, as they touch on basic EU rights.
Tusk's proposals will include a "red card" system that would allow 55 per cent of national parliaments to club together and stop proposed legislation out of Brussels, or make changes to it within 12 weeks of it being presented, a Downing Street source said early Tuesday.
"It ensures that the European Commission cannot just ignore the will of national parliamentarians and delivers greater democratic control over what the EU does," the source said.
One of the most controversial demands has been the restriction of in-work benefits for other European citizens during their first four years in Britain.
According to London, this is to be addressed through a so-called emergency brake on welfare payments to EU citizens that would apply if Britain can show that its social services system is overwhelmed.
The commission has made clear that "the UK's current circumstances meet the criteria for triggering the emergency brake," a spokesperson for Cameron said at the weekend.
But commission spokesman Margaritis Schinas urged caution on Monday, noting that any deal needs to be approved by all other EU member states.