Britain's Treasury chief says the economy could face a slowdown because of the uncertainty caused by the U.K.'s decision to leave the European Union.

Philip Hammond said Sunday that "we're going to have an unprecedented level of uncertainty, and that's one of the factors causing many commentators to predict that there will be a slowing of economic growth."

Hammond told ITV television that "we just have to plan to accommodate it."

Prime Minister Theresa May's government says it will trigger formal exit talks with the EU by March 31, but won't give away its negotiating position beforehand.

That has led to economic jitters, as well as speculation and lobbying by those who want to keep close ties with the bloc, as well as those who favor a decisive break.