Prime Minister David Cameron arrived at a summit of European leaders in Riga on Friday prepared for a discussion that could define his government — negotiating a new deal for Britain in the European Union.

Although he maintains that treaty changes are possible, he appeared to temper expectations of any quick solutions.

He said: “These talks will not be easy. They will not be quick. There will be different views and disagreements along the way. But by working together in the right spirit and sticking at it, I believe we can find solutions.”

However, other European leaders seems to downplay the likelihood of any deal being struck. German Chancellor Angela Merkel told the press that she did ” not think that is this evening’s subject,” while  European Commission president Jean-Claude Juncker said that the conference was ” not a meeting concerning UK membership.”

Cameron has given a “cast-iron guarantee” to hold an in-out referendum on Britain’s membership of the European Union by the beginning of 2018.

Most now expect he will try to hold it as soon as he can — possibly even next year — in order to take advantage of the momentum gained by the Conservatives in the party’s shock election victory and to avoid being caught up in the French and German elections in 2017.

For many businesses, this Brexit threat was the central concern during the election campaign amid concerns that an exit could disrupt trade with the Continent and isolate the UK. Moreover, Cameron himself says he doesn’t want the country to leave the EU, but to remain in under renegotiated terms.

In particular, Cameron wants to make it harder for EU migrants to claim benefits in the UK in order to lower the number of people coming to Britain from the Continent. He also hopes to open up discussion on EU regulation in order to remove “red tape.”

There’s a big problem with that idea, however: European leaders aren’t interested in renegotiating on what they see as the fundamental principles of the union.

In January Jean-Claude Juncker, the president of the European Commission, likened Britain’s relationship with Europe to a love affair that is fading with age.

He was very clear that principles such as right of citizens of EU countries to live and work in any member state were “red lines” that countries could not simply opt in and out of as they see fit.

In what could be viewed as a direct dig at Cameron’s renegotiation promises, he said:

“When one mentions the end of the free circulation of workers, there can be no debate, dialogue or compromise. We can fight against abuses — and national lawmakers can do that — but the EU lawmakers won’t change the treaties to satisfy the will of certain politicians.”

There is one piece of good news for Cameron though — it looks like the British people are becoming less and less keen on the idea of leaving: