WASHINGTON - President Barack Obama is calling for national unity ahead of Sunday's anniversary of the Sept. 11 attacks and reflecting on a decade that tested America's character. ‘The terrorists who attacked us that September morning are no match for the character of our people, the resilience of our nation or the endurance of our values,' the president said Saturday in his weekly radio and Internet address a day ahead of the 10th anniversary of the attacks. ‘We're doing everything in our power to protect our people,' he said. ‘And no matter what comes our way, as a resilient nation, we will carry on.' Obama, a state senator in Illinois at the time of the attacks, made a pilgrimage Saturday to Arlington National Cemetery with his wife, Michelle, to remember the dead of the Iraq and Afghanistan wars. They visited Section 60 of the cemetery, burial ground for service members killed in the two wars. Those conflicts have claimed 6,213 military personnel. At one gravesite, the Obamas stopped to talk with members of a family who appeared to be visiting a grave. The Obamas chatted a few minutes, posed for pictures and gave out handshakes and hugs. Then, hand in hand, they strolled along one of the rows between identical white tombstones, pausing at some markers. They met another family of visitors and stopped to chat with them, shake hands and take pictures. Intelligence officials have been working around the clock to determine the validity of a new threat of a possible Al Qaeda attack on New York or Washington timed to coincide with the Sept. 11 anniversary. Obama met his senior national security team in the morning to review the latest developments and ensure the US remains on a heightened state of vigilance during the anniversary commemorations. The Obamas planned to participate in a service project Saturday afternoon in the Washington area. On Sunday, the president is scheduled to visit New York City, Shanksville, Pennsylvania, and the Pentagon, the sites where hijacked planes struck 10 years ago. In the evening, he planned to speak at a memorial event at the Kennedy Center in Washington. In the weekly address, Obama sought a balance between remembering and moving forward. He also tried to summon the feeling of unity that existed after terrorists killed nearly 3,000 people. ‘They wanted to deprive us of the unity that defines us as a people, but we will not succumb to division or suspicion,' Obama said. ‘We are Americans, and we are stronger and safer when we stay true to the values, freedoms and diversity that make us unique among nations.' Obama thanked American troops who have served in the post-Sept. 11 wars in Iraq and Afghanistan. He praised the military successes that led to advances against Al Qaeda and the killing of the group's leader, Osama bin Laden. He also reaffirmed his commitment to winding down the conflicts he inherited. ‘Yes, we face a determined foe, and make no mistake, they will keep trying to hit us again,' Obama said. ‘But as we are showing again this weekend, we remain vigilant. We're doing everything in our power to protect our people.' Former New York City Mayor Rudy Giuliani, who gave the weekly Republican address, said the terrorists achieved their goal of killing Americans, but failed to destroy the American spirit. ‘The country was not broken, but rather, it was more united in the days after Sept. 11 than at any time in my lifetime,' Giuliani said. ‘We displayed heroic spirit in many ways, but perhaps the most heroic was the unity of spirit that we shared as Americans. The American people demonstrated one of the most basic values that we share — our love of freedom and the value we place on individual human life.' Without mentioning Obama by name, Giuliani also used his address to criticise the administration's policies, saying that America is safer, but not as safe as it should be. He criticised plans to remove troops from Iraq and Afghanistan under a set schedule. ‘American security requires a long-term military presence in the part of the world, where people and organizations are plotting to kill us,' he said.