WARSAW (Reuters) – Prime Minister David Cameron said on Thursday his plans to reform Britain’s ties with the European Union before a membership referendum had become more important because of a security crisis in the bloc.

Following a meeting with Polish Prime Minister Beata Szydlo in Warsaw to discuss his renegotiation plans, Cameron also said the two had agreed to try to find a solution to Britain’s demand to be able to curb welfare payments to EU migrants.

“Even on the most difficult issue of welfare we have agreed to work together to find a solution,” Cameron told reporters. “I believe with the type of political will I have seen here in Poland we can find a way.”