The newly inaugurated US President Donald Trump is due to meet with British Prime Minister Theresa May this coming week, the White House announced on Saturday.

The meeting with May, which is set to take place on Friday, will be Trump's first with a foreign leader as the long-standing US ally prepares to start negotiations to leave the European Union.

In an interview with the BBC's Andrew Marr on Sunday, May said she would use the opportunity to discuss the Britain's future trading relationship with the United States, as well as NATO and the challenges of combating terrorism.

May 'won't be afraid' to challenge Trump

Although she said she looks forward to expanding the "special relationship" between London and Washington, she said she wouldn't back down from speaking up if Trump says something "unacceptable."

"Whenever there is something that I find unacceptable I won't be afraid to say that to Donald Trump," May told the BBC.

May's interview came on the heels of massive women's protests against Trump that were held around the world, drawing millions of male and female demonstrators. In London alone, organizers estimated that 80,000 to 100,000 people took part in the march.

The British prime minister did not directly answer questions as to whether she would address some of the derogatory comments Trump has made about women. She did say that her presence in the meeting as a female world leader will be enough of a statement.

"When I sit down (with Trump) I think the biggest statement that will be made about the role of women is the fact that I will be there as a female prime minister," May said.

Meeting with Mexico

Trump will also meet with Mexican President Enrique Pena Nieto, Press Secretary Sean Spicer said on Saturday.

The two leaders spoke on the phone and scheduled to meet on January 31 to discuss trade, immigration and security, Spicer said.

Trump is committed to renegotiating the North American Free Trade Agreement (NAFTA), signed in 1994 with Mexico and Canada, and said he would withdraw from the deal if no "fair deal" is forthcoming, the White House website states.

Another point of contention lies in Trump's promise to build a wall on the southern US border to keep migrants out and make Mexico pay for it - possibly by blocking wire transfers out of the United States from Mexican nationals. Mexican officials have repeatedly said their country will not be paying for a border wall.

During his presidential campaign, Trump also called Mexican immigrants "rapists."

The Mexican president's office said that Pena Nieto congratulated Trump during his call and that both parties agreed to open "new dialogue."

rs/rc    (AP, AFP, dpa, Reuters)