AP - The producers of World Trade Centre are donating $US1.3 million ($A1.72 million) to the September 11 memorial, keeping a promise to give 5 per cent of the film's opening weekend box office receipts to help build it.
Another US$1.3 million from the weekend's proceeds will be split equally among three September 11-related charities, the World Trade Center Memorial Foundation said.
The Paramount Pictures film opened nationwide on August 9 and has earned more than $US50 million ($A65.98 million) at the box office. The movie stars Nicolas Cage and Michael Pena as police officers trapped for hours in the trade center rubble.
The film's producers had promised to donate 10 per cent of its August 9-13 box office proceeds to the foundation and the three charities.
The donation raises the private money available to build the memorial to $US132.3 million ($A174.6 million); the memorial's cost is put at more than $US650 million ($A857.8 million).
The foundation is expected to raise $US300 million ($A395.91 million).
The Port Authority, which owned the trade center, and the Lower Manhattan Development Corp. rebuilding agency are covering the rest of the costs.
Construction on the memorial began this year, and officials say it will open in 2009.
The other charities to split donations from the Oliver Stone film are Tuesday's Children, a services organisation for children who lost parents on Sept. 11; the Tribute WTC Visitor Center, created by a Sept. 11 family group and set to open next week; and the New York Police and Fire Widows' and Children's Benefit Fund.