LONDON (AP) — The Latest on the Brexit negotiations (all times local):

11:15 a.m.

The head of the International Monetary Fund says that a failure to agree on a Brexit deal "would have dear economic consequences."

Christine Lagarde told a news conference in London on Monday that she's a "desperate optimist" but that it is possible that Britain and the European Union will not have agreed on future relations before Britain leaves the bloc in March.

The IMF says that even if there is a deal, it would still come with economic costs for Britain, as it would mean more barriers to trade than the current situation. As part of the EU, Britain currently enjoys the freedom of goods, services, money and people to move across borders with 27 other countries in the region. Brexit will revoke some of those freedoms.

Lagarde said, "Whatever the deal is will not be as good as it is at the moment."

10:20 a.m.

British Prime Minister Theresa May is fighting back against opponents of her blueprint for Brexit, saying Parliament will have to choose between her proposal and crashing out of the European Union without a deal.

May said Monday on the BBC that if rebel lawmakers shoot down a deal between her government and the EU, "the alternative to that will be having no deal."

With just over six months until Britain is due to leave the 28-nation EU on March 29, May's Conservative government remains divided over how close an economic relationship to seek with the bloc.

Former Foreign Secretary Boris Johnson, who says Britain should make a clean break with the EU, wrote in Monday's Daily Telegraph that May's Brexit negotiations were heading for a "spectacular political car crash."