The White House has published the president's statement on its website.
"NOW, THEREFORE, I, DONALD J. TRUMP, President of the United States of America, do hereby proclaim September 11, 2019, as Patriot Day. I call upon all departments, agencies, and instrumentalities of the United States to display the flag of the United States at half-staff on Patriot Day in honor of the individuals who lost their lives on September 11, 2001", Trump announced.
Close to 3,000 people were killed and 6,000 wounded in the attacks as al-Qaeda terrorists* hijacked commercial airplanes and slammed them into the World Trade Centre in New York City and the Pentagon in Washington, DC. Another hijacked plane crashed in Shanksville, Pennsylvania.
The incident was the biggest terror attack in modern US history and caused at least $10 billion in infrastructure and property damage.
*Al-Qaeda is a terrorist organisation banned in Russia