President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE reportedly suggested to Spain's foreign minister that the country could build a wall across the Sahara in order to manage Mediterranean migration.

The Guardian reported Wednesday that Spain's Foreign Minister Josep Borrell said Trump made the suggestion during a previous meeting and that the president added, "The Sahara border can’t be bigger than our border with Mexico.”

The Sahara desert is approximately 3,000 miles wide from east to west, or about 1,000 miles longer than the U.S. border with Mexico. It extends beyond Spain's borders.

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Trump's reported suggestion may have been made when King Felipe and Queen Letizia visited the White House in June, accompanied by Borrell.

Spain has overtaken Italy and Greece as the main destination for migrants crossing the Mediterranean this year, with more than 33,600 arriving by sea so far, according to the International Organization for Migration, the United Nations’s migration agency.