German Chancellor Angela Merkel said Thursday that she can work with Britain to reform the European Union but it will not be “a piece of cake”, BBC reported.

Merkel, following a Downing Street meeting with British Prime Minister David Cameron, said both the nations could bring in laws to curb benefit tourism, as part of “overall European cooperation”. She is on a day-long visit to London.

Cameron, on the other side, said changes to the EU were “possible, achievable and doable”. He is keen to negotiate changes to Britain’s treaties with the EU ahead of a promised referendum on whether the country should remain in the organisation, which he wants to hold before the end of 2017.

He views Merkel as a key figure in achieving his aim.

Merkel addressed Parliament earlier and later had tea with the Queen at Buckingham Palace.