At their summit on 18-19 February, EU leaders will decide on whether to introduce a law that would allow member states to limit in-work benefits for migrants from elsewhere in the EU for up to four years.

This measure and others on eurozone governance, the role of national parliaments and Europe's competitiveness are part of the draft proposal published on Tuesday (2 February) by EU Council president Donald Tusk in response to British demands for EU reform.

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Although EU officials say all of the issues are difficult, benefits were considered the most difficult during the preparatory work that culminated with meetings between British prime minister David Cameron and European Council president Donald Tusk and European Commission president Jean-Claude Juncker in recent days.

Under the proposed deal, EU member states will be able to limit access to their social security system to EU workers "for a total period of up to four years".

"The limitation should be graduated, from an initial complete exclusion but gradually increasing access to such benefits to take account of the growing connection of the worker with the labour market of the host member state," the document says.

Exceptional situation

The duration of the initial period and extensions remain to be decided. The scheme will be open to all EU member states in order to bypass the risk of discrimination created by Cameron's original request to allow a ban on EU workers in the UK only.

Central and eastern EU states, where many migrant workers in the UK come from, said they would block any deal including a measure they consider discriminatory.

Under the proposals, the limitation can be authorised by the EU Council of member states by a qualified majority if one of them can demonstrate "an exceptional situation … on a scale that affects essential aspects of its social security system".

Matters such as how stress on the social system is assessed before the mechanism is triggered, as well as a more precise definition of a worker, in particular according to the level of revenue, are left to future legislation, to be proposed and adopted by the EU.

Under the plan, child benefits could also be indexed to the cost of raising children in the country where they live, not in the country where their parents live or work. The plan, which would be optional for member states, is a response to British concerns over the "exportation of child benefits" to other countries.

The draft document, which reiterates that member states "enjoy a broad margin of discretion to define and implement their social and employment policy", also follows the case law of the European Court of Justice and specifies that all EU citizens cannot falsely claim benefits.

Eurozone governance

In another difficult "basket" of British demands, the document drafted by Tusk clarifies the relations between eurozone and the non-euro countries.

While Cameron wanted to ring-fence the UK from decisions taken by the eurozone, the proposal guaranteed that "the competences, rights and obligations of member states whose currency is not the euro" would be respected, and that non-euro countries would not have to pay for "emergency and crisis measures addressed to safeguarding the financial stability of the euro".

The draft however specifies that "member states whose currency is not the euro shall not impede the implementation of legal acts directly linked to the functioning of the euro area and shall refrain from measures which could jeopardise the attainment of the objectives of the economic and monetary union".

France had said in recent days that preventing further eurozone integration would be a red line.

In the "sovereignty" basket, the draft contains Cameron's demand that the reference to "an ever closer Union" in the treaties is not "an equivalent to the objective of political integration".

But whereas the proposal recognises "that the United Kingdom, in the light of the specific situation it has under the treaties, is not committed to further political integration into the European Union", "the substance of this" would be incorporated in the treaties "at the time of their next revision".

More concrete could be the proposal to increase the role of national parliaments in the EU legislative process.

If a group of assemblies believed a legislative proposal went against the EU principle of subsidiarity, namely that decisions should be taken at the most local level possible, they could block it as long as they did so in the 12 weeks after its publication.

They could trigger the so-called red card if they represent 55 percent of the votes allocated to the national parliaments.

'I sure would opt in'

"I am convinced that the proposal is a good basis for a compromise," Tusk said in a letter accompanying the draft.

"To be, or not to be together, that is the question which must be answered not only by the British people in a referendum, but also by the other 27 members of the EU in the next two weeks," he said.

Cameron, for his part, said there was "more work to do" but assured "hand on heart" he was reaching his objectives.

"If I could get these terms for British membership I sure would opt in to be a member of the EU because they are good terms and they are different to what other countries have," he told an audience in an English factory.

The reference to the four-year ban on benefits, although under a flexible mechanism whose details still have to be elaborated, will help Cameron present the draft deal as a victory.

The proposal however falls short on several demands, including securing some elements of the agreement through EU treaty change, for example on benefits or on relations between euro and non-euro countries.

Most of the solutions proposed by Tusk in his document drafted with EU Commission services involve secondary legislation, and therefore further technical and political discussions.

For many countries, it was important to avoid going into primary law procedures, an EU diplomat told EUobserver.

Other member states are now examining the draft proposal. Their EU ambassadors and national "sherpas", EU government advisers, will meet on Friday (5 February) and on 11 February.

After that the most trying aspect of the negotiations will commence - addressing the difficulties and reservations of other EU leaders.