STOCKHOLM (AP) — Sweden's prime minister says a deal between Britain and the European Union within the envisioned two-year time frame is unlikely — and the U.K. will have to pay a big bill before it is allowed out the door.

Prime Minister Stefan Lofven tells The Associated Press in an interview that it will be "very tough" to get an agreement by 2019, the timeframe laid out in EU rules.

British Prime Minister Theresa May plans to invoke Article 50 of the key EU treaty, starting the two-year exit process, by March 31.

Lofven says it's "optimistic" to think the U.K. can be disentangled from the bloc and its web of laws, benefits and obligations, by March 2019.

He says it's "going to be very tough, to do all these things within two years."