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Republican presidential candidate Donald Trump.
The Republican presidential nominee, writing about how Europe was a "terrific place" for investment, argued at the time that the 2008 recession had made it clear "the global economy has become truly that - global."
Trump wrote that "cultures and economics are intertwined" in today's society and that it was necessary to "work with each other for the benefit of all."
"My concern is that the negligence of a few will adversely affect the majority," he wrote.
Trump continued: "In this case, the solution is clear. We will have to leave borders behind and go for global unity when it comes to financial stability."
The real-estate mogul concluded his op-ed writing that the future of the US and Europe "depends on a cohesive global economy."
"All of us must work together toward that very significant common goal," he declared.
Trump has been a strong critic of trade treaties, opposing the proposed Trans-Pacific Partnership deal and North Atlantic Free Trade Alliance, often finding himself at odds with members of his own party to do so. He has also cheered Great Britain's vote to leave the European Union, claiming parallels between his own political rise and the so-called Brexit.
And the billionaire has recently skewered his Democratic rival, Hillary Clinton, for privately expressing a desire for a borderless hemisphere, despite writing in his 2013 op-ed that it would be necessary to "leave borders behind."
A spokesperson for the Trump campaign did not immediately respond to a request for comment.
The unearthed comments came just hours before Trump was set to face off with Clinton in the final presidential debate. On Thursday, he trailed the former secretary of state by 6.9 points in the RealClearPolitics national average.