By Jenny Gross

ANKARA--British Prime Minister Theresa May on Saturday will meet Turkish President Recep Tayyip Erdogan in Ankara to discuss trade relations as she faces criticism at home for seeking to increase ties with the leader.

Mrs. May, who on Friday met with U.S. President Donald Trump , has said Britain is reshaping its role in the world as it leaves the European Union, including by renewing its relationship with both new allies and longstanding ones. In Washington, she and Mr. Trump committed to moving forward to lay the groundwork for a U.S.-U.K. trade deal.

"She thinks it's important and in the U.K.'s interest to engage with Turkey on a range of issues, from defense andsecurity cooperation to capitalizing on trade opportunities," a Downing Street official said ahead of her meeting with Mr. Erdogan.

Mrs. May has been criticized by those who see her as cozying up to leaders whose views are at odds with those of Britain.

Since the failed coup in July, Turkish authorities have purged more than 140,000 civil servants and military personnel accused of supporting alleged coup plotters. Thousands of them are under detention.

Tom Brake, a Liberal Democrat lawmaker, criticized Mrs. May for allying with Mr. Trump and Mr. Erdogan. "This is a deeply alarming sign of her priorities for diplomacy in post-Brexit Britain," Mr. Brake said.

The U.K. is Turkey's second largest export market after Germany, accounting for around 7% of the country's exports in 2015. But it is a relatively small market for the U.K., with Turkey buying less than 1% of British goods and services shipped overseas, suggesting thecountry may be a lower priority for the U.K. than the likes of India and the U.S.

Mrs. May is seeking clear commitments from countries around the world on trade agreements, in a move that could strengthen her hand when she starts negotiations on Britain's future trading relationship with Europe. But if Britain goes too far in negotiating deals, the government risks angering European leaders, who have warned the U.K. that it can't finalize trade deals while it is still a member of the EU. Britain's exit from the EU is targeted for March 2019.

Any future trade deal with Turkey could be complicated by Turkey's trading relationship with Europe. Turkey isn't a member of the EU but it is part of the bloc's customs union, meaning Turkish-made goods circulate freely within member states without tariffs and cumbersome border checks. EU rules require members to agree common tariffs to goods made outside the area's borders, meaning individual countries can't agree to tariff-lowering deals with third-party countries on their own.

Britain is currently a member of the customs unions, but Mrs. May has said she wants to pull out of the arrangement and the bloc's single trading market to give the U.K. free rein to strike its own trade accords. The government says the U.K. economy will prosper once it can make tailor-made trade deals based on British interests, rather than the interests of EU countries.

Jason Douglas in London contributed to this article.

Write to Jenny Gross at jenny.gross@wsj.com

(END) Dow Jones Newswires

January 28, 2017 06:36 ET (11:36 GMT)

Copyright (c) 2017 Dow Jones & Company, Inc.