BRUSSELS, June 26 — British Prime Minister David Cameron found his reform agenda sidelined at a tense EU summit yesterday as leaders warned he faces a tough negotiation ahead of a referendum on whether to leave the bloc.

As he walked into the summit dominated by Greece and migration, Cameron said it marked a “significant milestone” in Britain's bid to renegotiate ties with the European Union before a referendum due by the end of 2017.

Sources expect European leaders to discuss his proposals only briefly over dinner last night before agreeing to move to the next stage in the process — technical talks. The issue is thought likely to be mentioned briefly in the final summit communique.

Other European leaders at the summit are focused on trying to keep Greece in the eurozone and grappling with an influx of migrants from Middle East and African trouble spots, meaning substantial talks on reform will have to wait.

As he arrived for the high-stakes summit, EU President Donald Tusk warned that only changes which were “safe” for Europe would be considered.

“One thing should be clear from the very beginning — the fundamental values of the EU are not for sale and non-negotiable,” Tusk said.

Martin Schulz, president of the European Parliament, also fired a shot across the bows of Cameron, who has insisted the changes he wants require treaty change.

“I think treaty change is quite difficult and the UK government should not only exclusively focus on treaty change,” he said.

British officials accepted yesterday that any such change may not be implemented by the referendum but that Cameron would instead secure legally binding pledges that EU laws would be altered to include the reforms.

Meanwhile, Queen Elizabeth II used a state visit to Germany on Wednesday to warn that “division in Europe is dangerous.”

Months of work ahead

A senior EU diplomat speaking on condition of anonymity predicted that a comprehensive discussion of proposed reforms would have to wait until “the second half of the year.”

A senior EU official expected British reforms to take up one line in the summit communique.

“They will decide what is the timeframe and how this process should be organised in the four months to come,” the official added.

Cameron's official spokesman said what mattered was “the substance and that technical work gets under way before the summer.”

Senior EU civil servant Jonathan Faull, a Briton, has already been appointed to lead a taskforce in Brussels on the referendum.

The summit comes after several weeks of whirlwind diplomacy by Cameron since he won last month's general election in a bid to make his case for change to fellow EU leaders.

Downing Street expects he will have spoken to all 27, mostly in person, by the time the summit starts.

There is even a call scheduled with Greek Prime Minister Alexis Tsipras, whose own country faces an uncertain future in the EU because of its debt crisis.

As discussions enter the next stage behind closed doors, Cameron — who wants to stay in the EU if he gets the right changes — faces increasing pressure from his centre-right Conservative party to be clearer on exactly what he is pushing for.

Officials point to four broad areas of negotiation — improving competitiveness; ensuring fairness for non-eurozone countries; protecting sovereignty, including opting out of the EU's commitment to “ever closer union” and limiting access to benefits for migrants.

They have refrained from being more specific in public and Cameron's Europe Minister David Lidington has warned that doing so could prejudice the negotiation.

While the referendum must take place by the end of 2017, ministers are keen to hold it sooner if possible and some senior Conservatives now believe it will take place in the second half of next year. — AFP