Tusk: Deal on UK's EU renegotiation 'very tough'

At an emergency EU summit on migration in Malta, European Council President Donald Tusk referred to a letter he received from UK Prime Minister David Cameron, saying that "it will be really difficult to reach an agreement."

"Their requests are tough and this is why this matter was so interesting for me, but I have to say that it would be really difficult to find an agreement and, for sure, there is no guarantee that we can do it by December," said Tusk.

In his letter, David Cameron set out four demands at the heart of the UK's renegotiations: protection of the single market for Britain and other non-euro countries, boosting competitiveness by setting a target for the reduction of the "burden" of red tape, exempting Britain from "ever-closer union" and bolstering national parliaments, restricting EU migrants' access to in-work benefits such as tax credits. Once these demands are met, Cameron said he will campaign for Britain to stay in the EU.