BERLIN — The German and British leaders were meeting Friday amid tensions over how to resolve the eurozone debt crisis, while the head of the European Central Bank called for an end to delays in implementing EU rescue plans.

German Chancellor Angela Merkel, whose country has Europe’s biggest economy, has been a leading player in efforts to resolve the 17-nation eurozone’s crisis that have often been criticized as too hesitant.

British Prime Minister David Cameron travels to Berlin as Merkel seeks support for changes to European Union treaties that are meant to strengthen the eurozone but would need all 27 EU members’ approval — a potentially long and messy process.

Cameron said last week that “if the leaders of the eurozone want to save their currency then they — together with the institutions of the eurozone — must act now.”

Britain is a member of the EU but doesn’t use the euro. Cameron’s party is deeply skeptical about European integration.

Merkel insists that there’s no single quick-fix solution to the crisis. She has rejected the idea of jointly backed “eurobonds” and suggestions that the European Central Bank should step in with massive bond purchases to reduce the lending costs of countries such as Italy.

The ECB has also been reluctant to step up its so-far limited bond purchases. On Friday, bank president Mario Draghi expressed frustration at the slow pace of European leaders’ efforts to resolve the crisis.

A European summit last month agreed on a second bailout package for Greece and measures to increase the firepower of the bloc’s rescue fund, the (euro) 440 billion ($600 billion) European Financial Stability Facility.

Those decisions have yet to be translated into action and it remains unclear exactly how the EFSF will be leveraged.

Draghi noted that the EFSF was first launched more than 18 months ago and four weeks have passed since the last summit.

At a banking conference in Frankfurt, he asked: “Where is the implementation of these long-standing decisions?”

A further source of tension is Merkel’s desire to introduce a tax on financial transactions in Europe — an idea that has strong political support across the board in Germany but, with prospects of a wider global agreement thin, cuts little ice with Britain.

A senior Merkel ally voiced frustration earlier this week.

“The British are not members of the currency union, but they are members in Europe — and they too bear responsibility for Europe succeeding,” Volker Kauder, the parliamentary leader of her conservative bloc, said at a party conference.

“Only looking for their own advantage and not being prepared to put anything in themselves — that can’t be a message that we let the British get away with,” he added.

Merkel herself has sounded conciliatory, saying in a speech on Thursday that Cameron was right to focus on tackling Britain’s debt when he took office last year.

She also has insisted that she doesn’t want to see the 17-nation eurozone and the full 27-member EU grow apart in the crisis. Merkel said that issue requires “a great deal of political sensitivity.”

“We want a Europe with Great Britain, we want a Europe with a strong Poland of course,” she said, referring to another large EU country outside the euro.