President Bush vows in his latest campaign ad to "bring an enemy to justice before they hurt us again" although Usama bin Laden (search) remains at large and only one U.S. defendant, Zacarias Moussaoui (search), has been charged with crimes related to the Sept. 11, 2001 terrorist attacks.

"I can't imagine the great agony of a mom or a dad having to make the decision about which child to pick up first on September the 11th," Bush says in the 30-second television ad, which started airing Wednesday. "We cannot hesitate, we cannot yield, we must do everything in our power to bring an enemy to justice before they hurt us again."

Meanwhile, the Democratic National Committee launched a radio ad that also mentions the terror attacks and claims that Bush has distorted Sen. John Kerry's (search) record on terrorism in a Republican radio ad. That, the Democratic commercial says, is "beneath the office of president."

Bush's new TV commercial underscores his argument that his pre-emptive strike on Iraq was warranted in a post-Sept. 11 era and as commander in chief, he has pursued policies to protect the nation.

Appearing with his wife Laura in the ad, Bush also speaks of the emotions parents felt three years ago on the day of the attacks.

But the line about bringing "an enemy to justice" highlights the administration's pursuit of terrorists.

The Bush-Cheney campaign said Wednesday that two-thirds of bin Laden's Al Qaeda terrorist network has been "brought to justice" since the attacks and that the nation is safer today because of the president's policies. The Taliban regime in Afghanistan has been toppled and Al Qaeda's No. 3 leader, Khalid Shaikh Mohammed (search), has been arrested.

But bin Laden still evades capture nearly three years after the attacks and a key conclusion in last month's Sept. 11 commission report said that Al Qaeda's imitators pose a "catastrophic threat" to the United States.

Moussaoui's trial is on hold as an appeals court weighs how he can have access to key Al Qaeda witnesses that the U.S. government has captured. Moussaoui was charged in December 2001.

The ad comes as Bush and Kerry have traded criticism over the war in Iraq, with the Republican accusing his rival of an ever-changing position on the war and Kerry faulting Bush for misleading the American people and failing to assemble sufficient allied support.

Bush sends a message in the ad that he would strike again if America's security were questioned, stressing that "my most solemn duty is to lead our nation to protect ourselves." Bush has sought to persuade voters that they shouldn't replace the commander in chief.

The ad started running Wednesday on national cable networks and on local media markets in 19 competitive states.

Democrat John Kerry's campaign charged that an ad invoking the terrorist attacks was proof that Bush's re-election campaign "has reached the point of desperation" and was a sign that "Bush has lost credibility." "He can't speak to a single issue voters care about: not jobs, not health care, not deficits," said Chad Clanton, a Kerry campaign spokesman.

The DNC's independent expenditure office, which legally can't coordinate with Kerry's campaign, references the attacks in its new radio ad. The spot responds to one Bush is airing that argues that the Democrat's tough talk on terrorism doesn't square with his four-term Senate voting record on national security.

"We were altogether in this country after 9/11 and we all wish it had stayed that way," the DNC ad says. "But now President Bush is attacking John Kerry on terrorism and once again his facts are wrong."

The ad claims that Kerry fought to establish a Homeland Security department, while "Bush opposed it for almost a year after 9/11." Republicans argued that Democrats were the ones who stalled the department's creation because of pressure from unions, and that it was Kerry who skipped the vote to fund it in 2003.

The DNC is spending roughly $650,000 to run the radio ad in more than a dozen battleground states, compared to roughly $850,000 Bush paid to air his radio ad. Bush has far outspent Democrats on radio, spending at least $4 million compared to just thousands of dollars for Kerry.

Combined, Bush is spending at least $19 million on advertising this month, although his campaign is adding to its buy almost daily. Kerry is off the air until September as he saves money for the fall. However, through the first two weeks of August, Democratic groups will have spent $18 million to run TV ads that mostly assail Bush, countering his advertising.

One of those groups, the Media Fund, expanded its ad campaign to Wisconsin, West Virginia, Iowa and Oregon this week, bringing to nine the number of states where it's on the air. The group rolled out a TV ad in Ohio on Wednesday in which workers criticize Bush's jobs record.