(CNN) Sen. Bernie Sanders condemned "bullying and harassment of any kind" Saturday in an email urging people representing his 2020 campaign in the media to act respectfully.

"Let us do our very best to engage respectfully with our Democratic opponents - talking about the issues we are fighting for, not about personalities or past grievances," Sanders wrote. "I want to be clear that I condemn bullying and harassment of any kind and in any space."

The email, which a source provided to CNN Sunday, came less than a week after Sanders officially announced his candidacy for president . The letter dissuades supporters from using personal attacks on Sanders' behalf, saying that the campaign message and rhetoric needs to be the opposite of President Donald Trump's.

"We must never forget what this campaign is about and who our real opponents are," Sanders wrote. "They are the most dangerous president in modern American history and the powerful special interests who back his agenda."

Sanders, an Independent from Vermont who identifies as a Democratic Socialist, has committed to run and govern as a Democrat if elected. His refusal to run as a Democrat in his campaigns for the US Senate has been a sore spot for many in the party. He does caucus with the Democrats as a senator.