President Bush promoted his administration's plans to build an anti-missile system Tuesday, suggesting that the program's opponents are jeopardizing the country's safety.

Bush did not refer to Democratic rival John Kerry (search), who would rein in spending on the project.

"I think those who oppose this ballistic missile system don't understand the threats of the 21st century," the president told applauding workers at defense contractor Boeing in Pennsylvania, a crucial state in Bush's bid for re-election.

"We say to those tyrants who believe they can blackmail America and the free isioned by Ronald Reagan."

Bush said opponents of the system are "living in the past. We're living in the future. We're going to do what's necessary to protect this country.

It was the 32nd trip of Bush's presidency to Pennsylvania, a state that Vice President Al Gore won 51 percent to 46 percent in 2000. Gore won critically important Delaware County, where Ridley Park is located, 55 percent to 43 percent.

The Boeing plant where Bush spoke manufactures the CH-47 Chinook helicopter and the V-22 Osprey. The $40 billion Osprey program has been plagued by design flaws and other problems that led to crashes killing 23 troops in 2000. A redesign of the aircraft has solved or eased those problems, the Pentagon says.

Bush took a tour in a helicopter assembly building. He climbed inside a Chinook 47 helicopter that was being refitted and, at one point, used a wrench to tighten or loosen a screw.

The Pennsylvania trip is Bush's second appearance at a Boeing factory in five days.

Last Friday, the president said at a Boeing plant in Seattle that the United States would go to the World Trade Organization if necessary to stop European subsidies to Boeing competitor Airbus. Kerry said more than a year ago that the United States should subsidize Boeing just as European nations subsidize Airbus.

Responding to Bush's comments, the European Union said that it was willing to consider "disciplining" government support to European aircraft maker Airbus — but only if the United States does the same for Boeing.