By Paul Carrel
BERLIN (Reuters) - Germany is ready to be "extremely helpful" to British Prime Minister David Cameron in his renegotiation of Britain's membership of the European Union, a senior German official said on Wednesday, in a strong signal of support from Berlin.
Cameron has promised to renegotiate Britain's EU ties ahead of a membership referendum by the end of 2017. While he favours staying in a reformed EU, he has said he rules nothing out if he does not get the changes he wants.
German government officials have expressed alarm at the possibility of Britain leaving the EU -- a scenario they believe would leave the bloc severely weakened.
"The German government has a very great interest that Great Britain remains a member of the EU and in allowing Cameron to run a successful campaign," the government official said at a formal government briefing ahead of an EU summit on Thursday and Friday.
Britain's push for EU reform will be addressed at a summit working dinner on Thursday evening. The German official expected this week's summit to lay the foundations for an agreement on EU reform next February.
Limiting benefits that EU migrants to Britain are entitled to is the most contentious among Cameron's demands.
Pressed on the benefits issue, the German official said: "We will be very helpful."
"We have clear political guidance. We want Britain to stay in the EU," he added. "We can't accept everything but we will do what we can to accommodate Mr. Cameron."
A poll on Wednesday showed that British support for remaining in the EU will fall significantly if Cameron is not able to achieve safeguards for non-euro zone countries and curbs to welfare payments for migrants.
Some German government officials have stressed that they cannot convince other -- mainly eastern -- European states to drop their opposition to Britain's push for a four-year curb on welfare payments for EU migrants.
But they do want to keep Britain in the union, where they value its contribution on economic policy issues such as efforts to develop the bloc's internal market, and its weight on security matters.
"The UK must sit in the driver's seat, and not next to it," said another German government official, speaking prior to Wednesday's official pre-summit briefing.
(Additional reporting and editing by Noah Barkin)
