President Bush reaffirmed his administration's commitment to building an antimissile system, accusing opponents of the program of "living in the past."

Although Bush did not mention his Democratic rival by name on Tuesday, his speech here at a Boeing Co. plant included a thinly veiled attack on John F. Kerry's stance on missile defense. "I think those who oppose this ballistic missile system don't understand the threats of the 21st century," he told 1,400 cheering Boeing employees and supporters.

Kerry has said he would cut back spending on missile defense.

Bush delivered his speech after taking a tour of the defense contractor's plant, which manufactures CH-47 Chinook helicopters and the V-22 Osprey for the U.S. Army. He told workers that equipment manufactured at the plant was "made by the best hands in America" and thanked them for "giving our troops what is necessary to keep safe."

The president noted that last month Boeing engineers loaded the first missile interceptor into a silo in Alaska -- describing that as the beginning of a national shield "envisioned by Ronald Reagan."

Standing on a platform flanked by two Chinooks, Bush said foes of the missile system are "living in the past. We're living in the future. We're going to do what's necessary to protect this country. We say to those tyrants who believe they can blackmail America and the free world: You fire; we're going to shoot it down."

Kerry foreign policy adviser Rand Beers said in a statement that in the months before the Sept. 11, 2001, terrorist attacks, "Bush and his closest advisers were preoccupied with missile defense, and their misunderstanding about the threats we face continues to this day." He said Kerry was committed to developing an effective missile defense.

Striking a bullish tone, Bush also touched on issues such as education, values and the economy but devoted most of his speech to national security and the war on terrorism.

He said he was "disappointed" by Kerry's pledge to reduce U.S. troops in Iraq in six months if he is elected president. "I think that sends a terrible signal; after all, the enemy has to wait for six months and one day," he told the crowd. "It sends a bad signal to our troops over there. . . . It sends a bad signal to the Iraqis. They're wondering if America is going to cut and run."

Continuing his campaign theme that he can best be trusted in this era of terrorism, Bush said, "There's more to do to protect this country from the threats of the 21st century. If America shows uncertainty or weakness in this decade, the world will drift towards tragedy. This is not going to happen on my watch."

Mindful of Pennsylvania's highly coveted 21 electoral votes, Bush declared: "I also want to win Pennsylvania. I'm coming to this state and asking people for the vote," reminding supporters that it was his 32nd trip as president to the state.

Several demonstrators had earlier gathered at the plant's entrance and at an intersection a mile away. Some carried banners with antiwar slogans; one woman brandished a placard with "President Bush, you killed my son" written on it.

Michael Balzano, a Boeing consultant from Virginia, said the visit was an acknowledgement of the firm's role in the Iraq war. "It's good to see that being recognized," he said.

Democratic vice presidential candidate John Edwards's focus was on the economy, drawing enthusiastic applause during a town hall meeting in Fort Smith, Ark., when he argued that because of the Bush administration's policies, "we really do have two different economies."

Edwards, who spoke to about 150 people at the University of Arkansas at Fort Smith, called attention to the most recent jobs report, which showed a gain of 32,000 jobs in July, and a study last week by the Congressional Budget Office showing that Bush's tax cuts have primarily benefited the wealthy. "This is not an accident. . . . It is the intended result of the policies of this administration," Edwards said. "If you want to have two different economies in this country, one for people earning millions of dollars a year and one for everybody else, you should vote for George Bush. If you want to have one economy where everybody gets a chance to move up . . . you ought to vote for John Kerry and John Edwards."

Gov. Mike Huckabee (R) issued a statement saying that Edwards "still hasn't explained why he thinks Arkansans should vote for the most liberal ticket since George McGovern was the Democrat nominee." Bush narrowly won Arkansas in 2000.

This was Edwards's second visit to the state in 13 days, and he said that he, like many Arkansans, grew up in a small town and remembers "Friday night football and Sunday church."

But for the most part, voters here on Tuesday were more concerned about the economy. "I believe this year it will go for the Democrats because we've lost so many jobs," Joyce Rye, 67, a retired employee for Whirlpool, who drove from her home 25 miles away for the event. "There's a lot of people can't afford to buy medicine and they get just enough money that they can't get on the state Medicaid program. They're having a hard time."

Rod Jones, 47, a tool and die maker for American Standard and one of dozens of union members in the audience, also thinks the Democrats' chances are better this year because people are anxious about the economy. "It's a desperate situation," he said. "Bush needs to leave. He's done nothing for the average American person working."

Jones said Democrats should enlist former president Bill Clinton to get out the vote in his home state. "If Clinton would work Arkansas, Arkansas would go to Kerry hands down," Jones said. Edwards did not mention Clinton during his remarks.

Williams is traveling with Edwards.

President Bush brandishes a tool during his tour of a Boeing plant in Ridley Park, Pa., where he criticized Sen. John Kerry's lack of support for a missile defense system.Sen. John Edwards said at a town hall meeting in Fort Smith, Ark., that President Bush's policies are creating a two-tiered economy.