Ireland's prime minister says "complications" remain in Britain's attempt to negotiate a new deal with the European Union, but he's optimistic an agreement can be reached.

Enda Kenny says European Council President Donald Tusk will publish a paper next week on the U.K.'s four key areas. The most contentious is a plan to make migrants from other EU countries wait four years before they can claim some British benefits.

That runs counter to the principle of free movement within the 28-nation bloc.

After meeting Prime Minister David Cameron at Downing St. Monday, Kenny said "there are still complications with one or two" of the proposals, "but I think these are issues which can be sorted and can be agreed."

Britain will hold an EU membership referendum this year or next.