Berlin Mayor Michael Müller has just sent President Donald Trump a message about his proposed Mexican border wall. As the mayor of the iconic German city that was divided by an imposing wall for almost three decades, Muller is in good position to offer advice.

"Berlin, the city of the division of Europe, the city of freedom of Europe, cannot look without comment when a country plans to build a new wall,” Müller said in a statement Friday. “We Berliners know best how much suffering a division of an entire continent, cemented by barbed wire and wall, has caused. Millions of people have been seized by this division of life. In the end, we, the people, have overcome this division, and it is one of the 20th century's star-studded hours when, at the Brandenburger Tor, the most important symbol of the division, people conquered the Wall and then removed them piece by piece. The Brandenburg Gate stands for the spirit of freedom!"

Berlin's mayor just issued this message for Donald Trump. It's quite something. https://t.co/gIIOei6ttTpic.twitter.com/B8SgYZhhJ0 — Jeremy Cliffe (@JeremyCliffe) January 27, 2017

Trump began moves to deliver on his campaign promise to build a wall at the Mexican border this week, signing an executive order for federal agencies to begin constructing the nearly 2,000-mile structure.

When Trump said he would raise a 20 percent tax on Mexican imports to cover the cost of the wall, Mexican President Enrique Pena Nieto canceled his planned visit to the White House.

BREAKING: Mexican president cancels US trip over border wall spat with Trump https://t.co/sXrrR3rhp6 — RT (@RT_com) January 26, 2017

"Today, at the beginning of the 21st century, we cannot simply accept it if all our historical experiences are thrown over by those to whom we largely owe our freedom, the Americans,” Müller’s statement continued. “I appeal to the President of the United States not to go this way of foreclosure and exclusion. Wherever such borders still exist today in Korea, in Cyprus, they create unfreedom and suffering.”

Müller ended his statement with a reminder of the words of US President Ronald Reagan, who in 1987 called on Soviet leader Mikhail Gorbachev to take down the Berlin Wall. “Remember his words: 'Tear down this wall,'” Müller said. “And so I say: Dear Mr. President, don't build this wall!"