Bush's new advert infuriated the Democratic camp. Kerry's running mate John Edwards called it "despicable".

The new commercial aims to portray the Massachusetts senator, who is running neck-and-neck with Bush in opinion polls ahead of the November 2 election, as weak in the war on terror.

A female narrator accuses Kerry of being dangerously weak on national security, while a pack of wolves ? standing in for terrorists ? prowl menacingly onscreen.

"And weakness attracts those who are waiting to do America harm," the narrator says.

Stepping up the campaign

Bush also stepped up his attacks in campaign speeches in the battleground states of Ohio and Pennsylvania.

Bush seized on a comment by a senior Kerry foreign policy advisor that the war on terrorism declared after the September 11, 2001, strikes was a "just a metaphor".

"I've got news: Anyone who thinks we're fighting a metaphor does not understand the enemy we face, and has no idea how to win the war and keep America secure," he said.

"You cannot lead our nation to decisive victory on which the security of every American family depends if you do not see the true dangers of the post-September the 11th era," Bush said, adding attacks over Kerry's policies on taxes, health care, retirement funds and abortion for good measure.

Recent poll

Bush meanwhile gained on Kerry in a new Time magazine poll out on Friday.

If the November 2 election were held today, 51 percent of 1200 likely voters questioned between October 19 and 21 said they would vote for Bush, 46 percent for Kerry and two percent for independent consumer crusader Ralph Nader.

Last week's numbers were 48 percent for Bush, 47 percent for Kerry and three percent for Nader.

The Kerry campaign accused Bush of using "the politics of fear".

"They have stooped so low now that they are using a pack of wolves running around a forest trying to scare you and trying to scare the American people," Edwards, a senator from North Carolina, told a rally in Florida.

"The president is continuing to try to scare America in his speeches and ads in a despicable and contemptible way."

Kerry and the female vote

Kerry concentrated his campaign on the battleground state of Wisconsin and the key female vote.

The Democrat challenger was joined by Caroline Kennedy Schlossberg, daughter of assassinated President John F. Kennedy, as he made the case that Bush had deserted working women and "turned back the clock" on equal pay.

"The women of America can write the future of America if they go to the polls and make their voice heard," said Kerry in a speech at the University of Wisconsin.

"No one in the White House understands the challenges they face. No matter how tough it gets, no one in the White House seems to be listening," Kerry said.

Shoring up sluggish support among women is one of Kerry's key aims as he enters the final stretch of the campaign.

Women voted for Democrat Al Gore in the 2000 election by 54-43 percent but polls show Kerry struggling to match that. The Washington Post had Bush leading among women 50-46 percent in a recent poll.

"As you tuck your daughter in at night, you worry because you want her to go to college and have all the opportunities in the world ? but you don't know how you'll ever manage to afford it," Kerry said.

Kerry argued that soaring health care costs, job losses and tax cuts favouring the rich had hit women disproportionately.

High-profile Kerry supporters

The Democratic campaign has also used actress Sharon Stone, Dana Reeve, widow of the crippled 'Superman' star Christopher Reeve, members of the US women's soccer team and September 11 widow Kristen Breitweiser at campaign events.

At a rally in Madison, Wisconsin, Stone, the star of 'Basic Instinct', portrayed Kerry as the candidate of principle, the candidate that has the best interests of "our kids", at heart.

The rival candidates are locked in a desperate battle to win support in the 10 battleground states expected to decide the election.

Bush also went to Ohio and was to spend the night in Florida, which has 27 of the Electoral College votes that will decide the presidency. Kerry also headed for the southeastern state for events on Saturday.