Australian Governor-General Quentin Bryce has unveiled a new monument in New York dedicated to "the thousands of innocent victims" killed in the September 11 terror attacks.

A flagstone, featuring the Australian coat-of-arms, is located in the Queen Elizabeth II September 11th Garden in Manhattan's Hanover Square, near the World Trade Centre site.

The garden was created in 2005 as a memorial park for Commonwealth September 11 victims.

"This significant site of remembrance is dedicated to honouring the thousands of innocent victims of those horrifying attacks that our world witnessed on the 11th of September 2001," Ms Bryce said at the ceremony attended by family members of victims of the terror attacks.

"I want to offer my deep respect to members of Commonwealth nations who perished at that time, including 10 Australians who lost their lives on that dreadful, dreadful day.

"This garden sows seeds of friendship and peace and it preserves this poignant and tranquil park as a gathering place in New York City."

Queen Elizabeth II visited the garden and laid a wreath in 2010.