Senator John Kerry, accepting the nomination of the Democratic Party for president, has pledged wide-ranging reforms of the U.S. intelligence system and efforts to repair U.S. credibility in the world, while warning terrorists he will respond with force as necessary to protect America.

Senator Kerry was introduced at the convention by some of his fellow crew members from the small military boats he commanded during the Vietnam War.

Recalling his service in Southeast Asia, Mr. Kerry sent this message to anyone he said who might question his ability to lead.

"Let there be no mistake: I will never hesitate to use force when it is required. Any attack will be met with a swift and certain response. I will never give any nation or international institution a veto over our national security," he said.

Mr. Kerry also pledged efforts to strengthen what he called an overstretched and over-extended U.S. military, but described as equally important the re-building of alliances so the United States is, in his words, looked up to and not just feared.

"We need a strong military and we need to lead strong alliances. And then, with confidence and determination, we will be able to tell the terrorists: You will lose and we will win. The future doesn't belong to fear; it belongs to freedom," he said.

Referring to Iraq, and the way the Bush Administration justified military action to remove Saddam Hussein, Senator Kerry pledged wide-ranging reforms to the U.S. intelligence system, and repeated a theme he voiced frequently on the campaign trail.

"I will immediately reform the intelligence system - so policy is guided by facts, and facts are never distorted by politics. And as president, I will bring back this nation's time-honored tradition: the United States of America never goes to war because we want to, we only go to war because we have to," he said.

If elected in November, Mr. Kerry said, he will immediately implement the recommendations of the independent commission that investigated intelligence and security lapses leading to the September 11, 2001 terrorist attacks.

"We shouldn't be letting 95 percent of container ships come into our ports without ever being physically inspected. We shouldn't be leaving our nuclear and chemical plants without enough protection. And we shouldn't be opening firehouses in Baghdad and closing them down in the United States of America," he said.

As he painted a picture of challenges facing the United States, Mr. Kerry also dealt directly with the economy.

And pointing to economic successes under Democratic President Bill Clinton, he outlined key economic goals:

"We value jobs that pay you more not less than you earned before. We value jobs where, when you put in a week's work, you can actually pay your bills, provide for your children, and lift up the quality of your life. We value an America where the middle class is not being squeezed, but doing better," he said.

Former General Wesley Clark, who competed against Mr. Kerry for the Democratic nomination, had this message for Republicans who he asserted are trying to portray Democrats as unpatriotic.

"This soldier has news for you tonight. Anyone who tells you that any one political party has a monopoly on the best defense of our nation is committing a fraud on the American people," he said.

Senator Joe Biden of Delaware, the top Democrat on the Senate Foreign Relations Committee and a sharp critic of the Bush administration on Iraq, had this harsh criticism: "I believe this generation will look and wonder why this administration has squandered the opportunities that were before it," he said.

The conclusion of the four-day Democratic convention will return Senator Kerry to the campaign trail with visits to a number of U.S. states over a two week period.

His opponent in the November election, President Bush, will be re-nominated by Republicans at their convention in New York City at the end of August.