Trump suggested Spain build a wall across African Sahara to stop migrants, minister says Spain has no sovereignty over the desert.

BRUSSELS -- President Donald Trump urged Spain this summer to build a wall across the African Sahara to solve the migrant crisis in Europe, according to Spain’s foreign ministry.

A ministry official told ABC News that Spanish Foreign Minister Josep Borrell spoke at a lunch event this week in Madrid about Trump’s purported remarks on the desert, which Borrell said the president made during his June visit to the United States.

“The border with the Sahara cannot be bigger than our border with Mexico,” Borrell said Trump told him this summer, according to the ministry official.

The United States' border with Mexico spans nearly 2,000 miles, while the 3.5 million-square-mile Sahara is about 3,000 miles long and stretches across nearly a dozen North African countries.

Spain has two small enclaves in North Africa, Melilla and Ceuta, to which migrants do often try to gain entry by way of the those two land borders. It does not, though, have sovereignty over the desert.

The White House did not immediately respond to ABC News request for comment.

ABC News’ John Parkinson contributed reporting from the White House.