Since taking office in January, the 71-year-old leader has made a habit of publicly bashing mainstream media outlets like The New York Times, which he regularly denounces as "fake news" on his Twitter account.
"I urge the United States administration to refrain from delivering such attacks on the media," Harlem Desir, the media freedom representative of the Organization for Security and Co-operation in Europe, said in a letter to the White House.
"The US president's statements are deeply problematic in that they degrade the essential role the media plays in every democratic society, holding governments to account and offering a platform for a diversity of voices," read the letter addressed to US Secretary of State Rex Tillerson.
Desir highlighted remarks Trump made at a rally in Arizona on January 22, during which the billionaire accused the media of being "truly dishonest", "crooked" and of "making up stories".
"In addition to undermining the credibility of the media, such statements, especially those identifying the media as the 'enemy of the people', could also make journalists more vulnerable to being targeted with violence and abuse," Desir said.
The Vienna-based OSCE, an international election and war monitor, also keeps track of media freedom issues throughout the OSCE's 57 member states, which include the US and Russia.
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