Logistical and sovereignty considerations aside, Borrell said he was opposed to the principle of building walls to curb Europe's migration crisis during his speech, El Confidencial reported. The Spanish Embassy in Washington did not immediately respond to a request for comment, but the Spanish Foreign Ministry told Britain's Guardian newspaper that the accounts of Borrell's comments were accurate.
According to Josep Borrell, the president wants the European Union member country to emulating his infamous Mexico border policy.
Trump's pledge to build a wall across the 3,000-kilometre US-Mexico border became a central focus of the 2016 presidential campaign.
Almost 2,000 people have died attempting to make the journey across the sea to Europe in 2018 so far.
Borrell said when Trump was asked if he was aware of the size of the Sahara desert, the latter replied: "It can't be bigger than our border with Mexico".
Borrell continued: "Well, yes, it is way bigger than the border with Mexico, and in any case it wouldn't be very useful to do that".
Fact is the Sahara desert is 3,000 miles long, which is approximately 1,000 miles longer than the U.S. Mexican border.
Spain also has no border with the Sahara, meaning it would have to build the barrier on foreign land. Around a dozen countries lie wholly or in part within the Sahara, including Morocco, Tunisia, Libya, Mali, Mauritania, Egypt, Algeria, Chad and Niger.
It was unclear from the Spanish media whether Trump was speaking in jest when he made the purported comments.
While the date of Trump's suggestion was not noted, it is believed that it took place during Borrell's trip to the United States in June of this year.