BERLIN (Reuters) - German Chancellor Angela Merkel said on Monday she did not want to pressure Britain to slow or accelerate its exit from the European Union but she also made clear that informal discussions on Brexit could not begin until London applies to leave.

Britons stunned global financial markets and world leaders by voting in a referendum last Thursday to leave the EU. On Friday Prime Minister David Cameron said he would resign in October and that he would leave it to his successor to start the formal process to quit the EU by invoking Article 50.

“I have neither a brake nor an accelerator, rather I have the job of reflecting when this message (to leave the bloc) arrives about how exactly we implement it,” Merkel told a news conference.

The chief executive of Britain’s Vote Leave campaign, Matthew Elliott, has said that London should begin informal negotiations on a full settlement governing its post-exit relationship with the EU before invoking Article 50.

But Merkel, Europe’s most powerful leader who will play a key role in shaping the future relationship between Britain and the EU, dismissed such a possibility.

“We can’t begin informal talks without having the message (Article 50) from Britain. That is clear for me,” she said.

Asked if Britain could wait until a new prime minister is chosen to make the formal announcement about its intention to leave the bloc, Merkel said: “We can’t have a permanent impasse.”

“Britain remains a member of the European Union until an application (to leave) is submitted and then there will be long negotiations,” she added.

Merkel said she had “some understanding” for Britain taking time to analyse its situation and said she would discuss the matter with Cameron at a gathering of EU leaders in Brussels on Tuesday.