"11th September...two contrasting images come to the mind. Today we pray tributes to all those who lost their lives in gruesome 9/11 attacks. On this day in 1893, Swami Vivekananda delivered his historic speech in Chicago & won many hearts & minds," Prime Minister Modi tweeted.
He said Swami Vivekananda's speech in Chicago demonstrated the strength of India's rich culture and the power of universal brotherhood and harmony.
More than 2,750 people were killed when two passenger jets destroyed the Twin Towers on September 11, 2001.
While another jet slammed into the Pentagon, a fourth jet crashed in a field in Pennsylvania after those on board tried to overpower the hijackers.
Swami Vivekananda's speech at the first Parliament of the World's Religions in Chicagois considered among his most significant contributions to the world - so much so that a three-day world conference was organised to commemorate his 150th birthday in 2012.
The speech made him a 'hero' in the U.S. His opening lines "Sisters and brothers of America" earned him a two-minute long standing ovation from the audience.