BRUSSELS • British Prime Minister David Cameron has said he would unveil his long-awaited European Union (EU) renegotiation demands early next month, amid growing impatience from his European partners.

Mr Cameron will lay out the demands in a letter to European Council President Donald Tusk next month, ahead of major talks on his plans with fellow European leaders in December. The letter will be made public.

Speaking to reporters after talks with European Commission President Jean-Claude Juncker in Brussels on Thursday, Mr Cameron said the negotiations ahead of a referendum on Britain's EU membership, that he has promised by the end of 2017, were going well.

"The pace will now quicken and I will be again setting out the four vital areas where we need change, laying down what those changes will be at the start of November," he said.

"So we quicken the pace and quicken those negotiations in the run-up to the December council."

So far, Mr Cameron has only said the demands will cover: an opt-out from the bloc's drive for an "ever-closer union"; economic competitiveness; protecting countries that are not in the euro; and curbing welfare for EU migrants to Britain.

Until Mr Cameron has a deal he thinks is good enough to sell to the British public, his government is refusing to back either the domestic "in" or "out" campaigns that have launched over the past few weeks.

A British official said Mr Cameron would unveil the plans in the letter he will send early next month to Mr Tusk, who was hosting a summit attended by the British PM and the other 27 EU leaders in Brussels on Thursday.

"It will lay down the changes we want to see," the official said on condition of anonymity.

Mr Cameron also discussed his demands during Thursday's summit.

Mr Tusk welcomed Mr Cameron's decision to lay out his thinking in writing, saying real negotiations could then begin.

There has been increasing frustration at Mr Cameron's refusal to spell out exactly what he wants despite the launch of technical talks with the EU in June.

"We need clarity on what we're going to be discussing over the next few months," European Parliament President Martin Schulz said.

Belgian Prime Minister Charles Michel said EU leaders had repeatedly asked for more details, adding: "I still do not know what Mr Cameron wants and hopes for."

It has now been 21/2 years since the British PM announced his intention to seek reforms of the EU and then hold the referendum, which he has still not set a date for.

AGENCE FRANCE-PRESSE, REUTERS