Madrid, Spain—A wall across the Sahara desert. That’s what President Trump has advised the Spanish government to do to curb the migrant influx.

According to the Spanish Foreign Minister Josep Borrell, President Trump suggested the idea during the former’s visit to the U.S. He cited the pre-election promise to erect a wall at the American-Mexican border as evidence that people aren’t so opposed to such propositions as some might think. Borrell, however, quickly expressed his disagreement with the proposal.

He also stated that President Trump cited the length similarities between the two borderlines to support his suggestion.  The US-Mexico border, however, is 1,954 miles whereas the Saharan desert is more than 3,000 miles long. Furthermore, Spain couldn’t erect such a wall given the national sovereignty questions that would arise. Although Spain owns two small enclaves on North Africa, Ceuta and Melilla, the rest of the northern part of Sahara belongs to Morocco, Algeria, Tunisia, Libya, and Egypt (the vast Sahara covers more countries, but these are the ones a border wall would presumably affect).

Borrell has previously served as the President of the European Parliament and thus understands the debate’s tricky spots.

So far in 2018, more than 35,000 migrants have arrived in Spain, making it the largest receptor of immigrants in Europe. Most immigrants come from Nigeria, the Ivory Coast, Guinea, and Senegal. More tragically, however, 1,600 have perished during the treacherous crossing.

“The reason the traffic has become deadlier is that the traffickers are taking more risk because there is more surveillance exercised by the Libyan coastguards,” said Vincent Cochetel, United Nations High Commissioner for Refugees’s special envoy for the central Mediterranean.

“They are trying to cut the costs: it costs them more to keep those people here longer in their warehouses, under captivity,” added Cochetel.

“We are calling for the European authorities, in particular, to come up with a coordinated strategy whereby boats can be systematically disembarked in different parts of Europe and where asylum claiming conditions and reception centres are in place ready to receive those people who arrive,” said Matt Saltmarsh of the UNHCR.