VALLETTA, MALTA - FEBRUARY 03: British Prime Minister Theresa May arrives at the Grand Master's Palace on February 3, 2017 in Valletta, Malta. Theresa May attends an informal summit of the 27 EU leaders to brief them on her recent meeting with President Trump. She has secured a guarantee from Trump that he is 100% supportive of NATO and she will encourage the EU countries to contribute the agreed 2% of their GDP on defence. (Photo by Leon Neal-Pool/Getty Images)

VALLETTA, MALTA - FEBRUARY 03:  British Prime Minister Theresa May arrives at the Grand Master's Palace on February 3, 2017 in Valletta, Malta.   Theresa May attends an informal summit of the 27 EU leaders to brief them on her recent meeting with President Trump. She has secured a guarantee from Trump that he is 100% supportive of NATO and she will encourage the EU countries to contribute the agreed 2% of their GDP on defence.  (Photo by Leon Neal-Pool/Getty Images)

VALLETTA, MALTA - FEBRUARY 03: British Prime Minister Theresa May arrives at the Grand Master's Palace on February 3, 2017 in Valletta, Malta. Theresa May attends an informal summit of the 27 EU leaders to brief them on her recent meeting with President Trump. She has secured a guarantee from Trump that he is 100% supportive of NATO and she will encourage the EU countries to contribute the agreed 2% of their GDP on defence. (Photo by Leon Neal-Pool/Getty Images)

VALLETTA, MALTA - FEBRUARY 03:  British Prime Minister Theresa May arrives at the Grand Master's Palace on February 3, 2017 in Valletta, Malta.   Theresa May attends an informal summit of the 27 EU leaders to brief them on her recent meeting with President Trump. She has secured a guarantee from Trump that he is 100% supportive of NATO and she will encourage the EU countries to contribute the agreed 2% of their GDP on defence.  (Photo by Leon Neal-Pool/Getty Images)

VALLETTA, MALTA - FEBRUARY 3: British Prime Minister Theresa May (R) attends the unofficial European Union summit as it begins with the attendance of other European Union delegates and heads of states on February 3, 2017 at Grandmaster's Palace in Valletta, Malta. European Union leaders will discuss illegal immigration into Europe. (Photo by Dursun Aydemir/Anadolu Agency/Getty Images)

VALLETTA, MALTA - FEBRUARY 3: British Prime Minister Theresa May (R) attends the unofficial European Union summit as it begins with the attendance of other European Union delegates and heads of states on February 3, 2017 at Grandmaster's Palace in Valletta, Malta. European Union leaders will discuss illegal immigration into Europe. (Photo by Dursun Aydemir/Anadolu Agency/Getty Images)

VALLETTA, MALTA - FEBRUARY 03: Delegates from the EU Informal Summit gather for the family photo on February 3, 2017 in Valletta, Malta. Theresa May attends an informal summit of the 27 EU leaders to brief them on her recent meeting with President Trump. She has secured a guarantee from Trump that he is 100% supportive of NATO and she will encourage the EU countries to contribute the agreed 2% of their GDP on defence. (Photo by Leon Neal-Pool/Getty Images)

VALLETTA, MALTA - FEBRUARY 03: Delegates from the EU Informal Summit gather for the family photo on February 3, 2017 in Valletta, Malta.   Theresa May attends an informal summit of the 27 EU leaders to brief them on her recent meeting with President Trump. She has secured a guarantee from Trump that he is 100% supportive of NATO and she will encourage the EU countries to contribute the agreed 2% of their GDP on defence. (Photo by Leon Neal-Pool/Getty Images)

VALLETTA, MALTA - FEBRUARY 3: British Prime Minister Theresa May (L), Belgian Prime Minister Charles Michel (C) and Prime Minister of Luxembourg, Xavier Bettel (R) chat during an informal European Union summit with the attendance of European Union delegates and heads of states on February 3, 2017 at Grandmaster's Palace in Valletta, Malta. European Union leaders will discuss illegal immigration into Europe. (Photo by Dursun Aydemir/Anadolu Agency/Getty Images)

VALLETTA, MALTA - FEBRUARY 3: British Prime Minister Theresa May (L), Belgian Prime Minister Charles Michel (C) and Prime Minister of Luxembourg, Xavier Bettel (R) chat during an informal European Union summit with the attendance of European Union delegates and heads of states on February 3, 2017 at Grandmaster's Palace in Valletta, Malta. European Union leaders will discuss illegal immigration into Europe. (Photo by Dursun Aydemir/Anadolu Agency/Getty Images)