The rally to be organised at Franklin D. Roosevelt (FDR) Four Freedoms Park in New York city, will mark the formal launch of her poll campaign.
She will address her first big campaign rally in the city. She is likely to be joined by husband Bill and daughter Chelsea in the family's first joint appearance of the campaign.
Thousands of supporters thronged Roosevelt Island, a tiny slither of land in the East River between Manhattan and Queens.
Clinton announced her long-expected presidential bid in an April video. She is seeking a Democratic presidential nomination to run for the White House in 2016. If elected, she would be the first woman president of the United States. This is her second presidential bid. In 2008, she lost in the Democratic Party primaries to current US President Barack Obama.