New York - Seven years after the September 11 terrorist strikes, New Yorkers on Thursday will remember the attacks that killed more than 2,700 people with the destruction of the World Trade Center's twin towers.

The city will observe the anniversary with renewed calls for vigilance against the constant threats of new terrorist attacks. Names of the dead will be read yet again.

The presidential nominees of both US major parties, Republic Senator John McCain and his rival, Democratic Senator Barack Obama, plan to attend ceremonies at Ground Zero, site of the destroyed towers.

Both candidates have agreed to call off their election rhetoric and suspend campaign television ads on that day out of respect for the dead from the 9/11 attacks, which targeted New York and Washington.

McCain and Obama issued a joint statement this week: "All of us came together on 9/11 - not as Democrats or Republicans but as Americans. We were united as one American family. On Thursday, we will put aside politics and come together to renew that unity."

The emphasis on the seventh anniversary has shifted to educating new generations about terrorist threats and the way families of victims survive the loss of loved ones.

The National September 11 Memorial & Museum this week unveiled programmes for classroom remembrances, distributed to selected schools across the United States. The outreach scheme will identify teachers to work in partnership with the memorial foundation to teach in classrooms about the attacks on September 11, 2001.

The memorial - for the nearly 3,000 victims of the 2001 terrorist attacks against New York and the Pentagon defence headquarters outside Washington, plus the prelude attack of the 1993 the World Trade Center truck bombing - is being built at Ground Zero, site of the original towers.

The memorial, designed and created by Michael Arad and Peter Walker, consists of two pools resting on the original two footprints of the 100-storey twin towers, which collapsed soon after being struck by hijacked airliners on September 11.

But construction costs have soared to nearly 1 billion dollars, forcing several reviews of the plan and delay in the construction of the memorial.

Sonnet Takahisa, education director for the Memorial & Museum, said: "The record of the events of September 11, the significance of those events, and our understanding of their impact are still evolving. We know that teachers feel ill-prepared to address 9/11 in their classrooms, and we hope to provide resources for teachers to use that will encourage and facilitate discussion."

Among material offered for classroom remembrances are documentaries recounting the events of 9/11 from the perspectives of family members, survivors and rescue workers.

US classrooms currently have no formal curriculum on 9/11.

The new World Trade Center, also besieged by soaring construction costs and constant reviews to make it an attack-proof fortress, will not be completed until after 2011, two years later than originally planned. A Freedom Tower will adorn the center at 1,776 feet (592 metres), a height chosen to recall the the US Declaration of Independence of 1776.

The 9/11 attacks killed more than 2,700 people in New York, including 300 firefighters and police trapped after rushing into the towers to save the thousands of people working inside. The trauma has lingered with thousands of New Yorkers who lost friends or relatives or who continued to suffer mentally or physically.

New York City Mayor Michael Bloomberg recently launched a programme to reach out to New Yorkers who still suffer health problems related to the terrorist attacks, with ads spanning television, radio and print media. The programme is part of a 5- million-dollar campaign to provide free health care to those who need help.