NEW YORK (AFP) - John McCain and Barack Obama declared a truce Thursday in their rancorous White House campaign, joining sombre Ground Zero ceremonies on the seventh anniversary of the 9/11 terror strikes. A moment of silence opened ceremonies at the side of the giant pit where the World Trade Centre towers once stood, followed by the reading of almost 3,000 victims' names. New York Mayor Michael Bloomberg said September 11, 2001 - when Al-Qaeda-hijacked airliners demolished the Twin Towers and crashed into the Pentagon and a field in Pennsylvania - was the day the United States "broke". Choking on tears, victims' relatives read out names of the dead. A string quartet, alternating with a classical guitar and flute, played mournfully in the background. The patriotic upswell provided a rare moment of unity in a country less than two months from the end of an increasingly divisive presidential race. McCain and Obama suspended advertising. However, statements issued by both men failed to steer entirely clear of political spin. Obama called 9/11 the day "Americans across our great country came together to stand with the families of the victims" and said, "let us renew that spirit of service and that sense of common purpose." However, the Democratic candidate pointedly referred to Republican President George W Bush's failure to make good on a promise soon after 9/11 to apprehend Al-Qaeda chief Osama bin Laden. "Let us remember that the terrorists responsible for 9/11 are still at large, and must be brought to justice," said Obama, whom McCain charges has little foreign policy and security experience. McCain paid tribute to those on United Flight 93, who assaulted their hijackers over Pennsylvania and crashed the plane before it could reach its target - speculated to have been the seat of the US Congress in Washington. He declared himself "in awe" of the mid-skies uprising. At Ground Zero, survivors, who wore white ribbons pinned to their chests, often broke off to add brief tributes as they read the names of dead relatives. One fought to control himself as he condemned the "cowardly men" who killed his loved one. At the Pentagon, thousands joined Bush and US Defence Secretary Robert Gates to dedicate the first September 11 memorial. Former defence secretary Donald Rumsfeld joined President George W Bush and US Defence Secretary Robert Gates as a flag was raised over the memorial. A Marine Corps bugler played taps from the roof where fire-fighters had unfurled an American flag while the building burned after the attack. Bureaucratic wrangling has continuously delayed plans to build a replacement for the World Trade Centre, a failure that symbolises popular frustration with the inability to catch Osama bin Laden and extricate troops from Iraq and Afghanistan. Ground Zero remains nothing more than a huge hole on prime real estate in lower Manhattan and the first steel beams for a planned Freedom Tower went in only this week. Nearly 3,000 people were killed in the deadliest attacks ever on US soil. A simple plaza, the memorial is dotted with bench-like units cantilevered over an individual reflecting pool, each inscribed with the name of a person killed in the attack on the Pentagon. The units representing the 59 people killed on American Airlines Flight 77 are inscribed so that a visitor will face the sky when the reading the name of the person to whom it is dedicated.