In March 2018, after his departure as German foreign minister, Gabriel published an opinion piece about the future of the relations between Turkey (under AKP rule) and the West, where he advocated for an inclusive stance towards Turkey and criticized the policy of the United States in that regard. In February 2020, he joined around fifty former European prime ministers and foreign ministers in signing an open letter published by British newspaper "The Guardian" to condemn U.S. President Donald Trump’s Middle East peace plan, saying it would create an apartheid-like situation in occupied Palestinian territory.