WASHINGTO - US President Barack Obama called on Americans to renew our common purpose Friday as he marked the eighth anniversary of the Sept 11, 2001 terror attacks. Speaking under rainy skies at the Pentagon, where 184 people died when American Airlines Flight 77 slammed into the facility, Obama said, On a day when others sought to sap our confidence, let us renew our common purpose; let us remember how we came together as one nation, as one people, as Americans, united not only in our grief but in our resolve to stand with one another, to stand up for the country we all love. Obama, who designated Sept 11 as a national day of remembrance and service, said coming together as a nation is the strongest rebuke to those who attack us as well as paying the highest tribute to those who died. That is our calling today and in all the Septembers still to come, he said. Admiral Michael Mullen, Chairman of the US Joint Chiefs of Staff, said Americans shared common sorrow for the lives lost in Washington, New York and Pennsylvania. Our grief is real and it is warranted, he said. But if I may, let me ask and let me urge that we look upon this day not only with sorrow, but also with hope for the future that those we honour wanted us to have, and gratitude for the life they wanted us to live. Words are inadequate to remove the pain of that loss, US Defence Secretary Robert Gates said, but in the lives of those patriots, we can find some solace. After their remarks, Obama, Mullen and Gates participated in a wreath-laying ceremony. The eighth anniversary of the 9/11 attacks on the World Trade Centre in New York City was observed in services amid a steady downpour of rain on Friday. Hundreds were on hand for the ceremony in Lower Manhattan to hear the names of over 2700 people who perished read by friends and loved ones. Four bells were tolled during the ceremony, with the first marking the time the initial plane struck the World Trade Centres North Tower. US Vice-President Joe Biden spoke after the second bell sounded. He told the crowd, (T)here is a special fraternity for those of us who have lost spouses and children. Biden was referring to his first wife and infant daughter who were killed years ago in a car crash. Reuters/AFP add: US President Obama sought to rally Americans behind the war in Afghanistan as opinion polls show faltering public support for the conflict. Let us renew our resolve against those who perpetrated this barbaric act and plot against us still, Obama said at a sombre ceremony attended by about 500 people under rain-filled skies at the Pentagon. In pursuit of Al-Qaeda and its extremist allies we will never falter (in its battle against Al-Qaeda), he said, before laying a wreath at a memorial for those killed at the Pentagon, calling for new national resolve to fight terrorism. Many choked back tears as they went through the litany against a background of sombre ceremonies in the US. This is not the rain, Im sorry. This is tears, one man said, clutching a photograph of his lost relative, the rainy weather so different from that crisp, autumn day eight years ago. Obama lamented that passing time had not dulled the pain of the loss of nearly 3,000 lives in a terrible instant, as he led national commemorations of the worlds worst terror attack for the first time as President. Mindful that the work of protecting America is never finished, we will do everything in our power to keep America safe, he said. Obama, who opened a day of national ceremonies by observing a moments silence at the White House, said that eight Septembers have come and gone since the attacks, but grief still lingered. No turning of the season can diminish the pain and the loss of that day. No passage of time and no dark skies can ever dull the meaning of this moment. Obama spoke to a crowd of relatives of the 184 people killed at the Pentagon when a hijacked airliner turned one side of the building into a fireball, and laid a wreath at the memorial. The US President led a moment of silence to launch eighth anniversary commemorations of the September 11 attacks. Earlier, at exactly 8:46 am (1246 GMT) when the first plane piloted by Al-Qaeda hijackers slammed into the North tower of New Yorks World Trade Centre, Obama and First Lady Michelle Obama stood with heads bowed outside the White House. Ceremonies were also held in New York, at the Pentagon and in a Pennsylvania field where a fourth plane crashed short of its target. At New Yorks Ground Zero, all that is left of the two huge towers that were toppled in wave of fire and debris by fuel-laden planes, volunteers read the names of the 2,752 people killed in the strike at the heart of US might. Obama stepped out in front of the South Portico of the White House, with First Lady Michelle Obama, who was wearing a black dress. After three chimes played by a US Marine in ceremonial dress, the first couple bowed their heads and observed the moment of silence, joined by around 150 members of the White House staff. In a message carried on the front page of the New York Daily News, Obama declared we are all New Yorkers and that the attacks will be forever seared in the consciousness of our nation. The President wrote that his controversial and increasingly unpopular war in Afghanistan was part of his strategy to take the fight to the extremists who attacked us on 9/11. Washington, he said, was committed to preventing nuclear weapons proliferation and to ensuring that all loose nuclear weapons be accounted for and secured within four years. Earlier, the US Coast Guards set off a security scare with a routine training exercise in the heart of the US capital on the anniversary of the Sept 11 attacks. Initial media reports that the Coast Guard had fired on a boat on the Potomac River were based on overhead radio calls made over a training frequency, the Coast Guard said in a statement. Police and federal law enforcement officials said the incident on the Potomac River near the Pentagon was a training exercise and no shots were fired despite early reports that several rounds had been shot at a suspicious boat. Coast Guard Vice Admiral John Currier said the reports were based on overheard radio calls made on an open training frequency, including authorities verbally simulating gunfire. Somebody said bang, bang on the radio, he said. This was a routine, low profile, normal training exercise, he told a news conference. The radio intercept generated intense media coverage and interest, justifiably so, but I think what happened was we saw this spiral out of control.