Republican President George W. Bush and his Democratic opponent, John Kerry, are charging into the final week of the U.S. campaign for the White House trading increasingly tough charges on the continuing conflict in Iraq. Former President Bill Clinton, who is recovering from heart surgery, joined Senator Kerry Monday on the campaign trail.

Senator Kerry seized on a news report in The New York Times newspaper that detailed the disappearance of 350 metric tons of explosives from a military base in Iraq.

Mr. Kerry says the materials could be in the hands of terrorists who want to kill American troops. "This is one of the great additional blunders of Iraq," he said. "The unbelievable incompetence of this administration, step after step, has put our troops at greater and greater risk, over-extended the American military, isolated the United States, put a greater financial burden on the American people. George W. Bush has failed the test of commander in chief."

Former Democratic president Bill Clinton, in his first campaign appearance since undergoing heart surgery last month, joined Senator Kerry in Pennsylvania, an important eastern state where public opinion polls show the race is very close.

Mr. Clinton focused his speech on domestic issues like jobs. "On the economy we have just lived through four years of the first job losses in 70 years, record bankruptcies, middle class incomes declining and poverty going up," he said. "In Pennsylvania alone you have lost 70,000 jobs compared with the 219,000 you gained by this time when that last fellow was president - me (laughs and applause)."

Democratic Party strategists are hoping Mr. Clinton's appearance in the final days of the campaign will provide a jolt of excitement for Mr. Kerry and attract undecided voters that supported the Clinton presidency.

Meanwhile, President Bush took his campaign to the western state of Colorado, another state where polls show a very close race.

He slammed Senator Kerry for sending what he called the wrong message about Iraq. "On Iraq, my opponent has a strategy of pessimism and retreat (boos). He has talked about artificial timetables to pull our troops out. He has sent the signal that America's overriding role in Iraq would be to leave, even if the job is not done," he said. "That sends the wrong message. It sends the wrong message to Iraqis who need to know that America will not cut and run.."

Mr. Bush charged that Senator Kerry's goal is to go back to the mindset of the 1990s, when he said terrorism was seen as a nuisance that was fought with subpoenas and a few cruise missiles.

Without referring to former president Clinton by name, President Bush said the apparent calm during the time he was in office was only what Mr. Bush called a shallow illusion of peace. "We know that throughout the 1990s the terrorists were training and plotting against us. They saw our complacency as weakness and so their plans became more ambitious and their attacks more deadly until finally the twin towers became ground zero and the Pentagon was in flames," he said. "My outlook was changed on September the 11th."

Surveys continue to show the race between President Bush and Senator Kerry is extremely close and possibly heading toward a photo finish like the contest four years ago.