US Vice-President Dick Cheney has lashed out at Democratic candidate John Kerry on the third day of the Republican convention in New York.
Mr Cheney said that in his 20 years in the senate Mr Kerry had repeatedly made the "wrong call" on national security, and was indecisive.
By contrast, Mr Cheney went on, George W Bush made "some of the hardest decisions" a president can face.
The speech comes on the third day of a convention marked by street protests.
Mr Cheney on Wednesday said the threat of future terror attacks made the 2004 election "one of the most important, not just in our lives but in our history".
He told roaring Republican delegates at Madison Square Garden conference hall that John Kerry did not "appear to understand how the world has changed since 11 September 2001.
"He talks about leading a 'more sensitive war on terror,' as though al-Qaeda will be impressed with our softer side," the vice-president railed.
He also stressed what he described as inconsistencies in Mr Kerry's voting record.
"Although he voted to authorise force against Saddam Hussein, he then decided he was opposed to the war, and voted against funding for our men and women in the field," Mr Cheney said.
"His back and forth reflects a habit of indecision, and sends a message of confusion."
A handful of protesters broke into the convention venue
Mr Cheney contrasted this with Mr Bush's leadership.
"I have seen him face some of the hardest decisions that can come to the Oval Office - and make those decisions with the wisdom and humility Americans expect in their president."
Earlier, keynote speaker Zell Miller, a Democratic senator from Georgia who is backing Mr Bush, also launched a blistering attack on the democratic candidate.
"Senator Kerry has made it clear that he would use military force only if approved by the United Nations," Mr Miller said.
"Kerry would let Paris decide when America needs
defending. I want Bush to decide."
Other speakers on Wednesday night included Michael Reagan - son of the late President Ronald Reagan - and Pennsylvania Senator Rick Santorum.
Mr Kerry repeated his attacks on Mr Bush as a war leader on Wednesday.
He told fellow veterans in Tennessee that in Iraq, he "would have done everything differently".
Earlier on Wednesday thousands of people staged a peaceful demonstration blaming Mr Bush's policies for job losses.
A three-mile (five-km) "unemployment line" snaked through New York, with protestors holding up leaflet reading "The next pink slip could be yours" - a reference to the paper notices given to those who are laid off.
The orderly protest was in sharp contrast to clashes between anti-Bush activists and police in recent days, which led to about 1,500 arrests.
Demonstrators also disrupted a Republican youth meeting in the conference hall.
A speech by White House Chief of Staff Andrew Card
was briefly interrupted when about 10 Aids activists blew whistles and chanted "Bush kills".
Police moved to remove the protesters.