Americans mark the fifth anniversary of the September 11 attacks today with somber ceremonies across the country and at the sites of the devastation in New York, Washington and Pennsylvania.

The milestone has revived traumatic memories of the day when nearly 3,000 people were killed by al Qaeda and has sharpened an election-year debate over whether America, caught in a vicious conflict in Iraq, is any safer.

His approval ratings weighed down by the unpopular Iraq war, President George W. Bush planned to attend the ceremonies at the sites and use the anniversary to renew his vow to pursue the war on terrorism.

"There's still an enemy out there that would like to inflict the same kind of damage again," Bush said on Sunday after visiting Ground Zero in New York where the World Trade Center's twin towers had stood.

He said the anniversary was "also a day of renewing resolve."

The hijacked airplane attacks on a crisp late summer day transformed Bush into a war president and he initially received high marks from Americans by attacking al Qaeda and the Taliban in Afghanistan.

But the warm glow cooled as American casualties mounted in the Iraq war and the hunt for al Qaeda leader Osama bin Laden foundered.

Facing the prospect that Democrats could wrest control of Congress from his fellow Republicans in November elections, Bush has been pushing his national security credentials as he did successfully during his 2004 re-election campaign.

While the White House insisted the anniversary ceremonies a 9 p.m. EDT (0100 GMT Tuesday) Oval Office speech by Bush were not about politics, images of the commander-in-chief in solemn remembrance are a respite from the drumbeat of criticism about the Iraq war.

Bush said he and wife Laura approached Monday's anniversary "with a heavy heart. It's hard not to think about the people who lost their lives on September the 11th, 2001."

Bush will meet firefighters in New York, visit Shanksville, Pennsylvania, where hijacked United Flight 93 crashed after a passenger revolt, and attend ceremonies at the Pentagon.

The fifth anniversary has generated a heated debate over whether America is safer. Bush, Vice President Dick Cheney and other top officials say they believe security has improved.

But Richard Ben-Veniste, a member of the 9/11 commission that investigated the attacks, said the failure to bring Osama bin Laden to justice makes many Americans feel less safe.

"We have not killed or captured Osama bin Laden five years after 9/11. And he remains the central focus spiritually, ideologically, if not operationally for Islamic radicals who mean to kill us," he told ABC News' "This Week" program.