DETROIT (AP) - As tractor-trailers rumbled across the U.S.-Canada border behind them, President Bush and Canadian Prime Minister Jean Chretien reported progress in tightening security at crossings while keeping goods flowing between the world's largest trading partners. ``America and Canada face new threats to our security. It's the new reality of the 21st century,'' Bush said. ``This great and peaceful border must be open to business, open to the people and it's got to be closed to terrorists and criminals.'' Added Chretien: ``We want to ensure the threat of terror will not undermine the security of our citizens or hold our economies hostage.'' The two leaders announced the launch Monday of a program meant to cut red tape for carriers moving in both directions while ensuring their payloads pose little security risk. They opened registration for the Free and Secure Trade Program, which will expedite the clearance process for approved carriers when it is up and running this December at six crossings. The program is meant to keep trade humming to and from this vital industrial region, where a thick blanket of air pollution hung in the air Monday. Restrictions after the terrorist attacks snarled traffic at the border here and resulted in parts shortages, causing some temporary shutdowns at assembly plants operated by General Motors Corp., Ford Motor Co., DaimlerChrysler AG, Toyota Motor Sales Inc. and American Honda Motor Co. Trade averages $1.3 billion a day between the countries, and some 6,000 trucks cross the bridge into Detroit every day. They continued barreling across the Ambassador Bridge, with minor restrictions, as Bush and Chretien spoke. Some 200 million people cross the border annually, and the two leaders said they were expanding a program that provides dedicated fast lanes for preapproved, low-risk drivers. The two countries began accepting applications for the border crossing here, and by the end of next year, the program - called NEXUS - should be in operation at all high-volume crossings. The measures were part of a 30-point plan that the two countries endorsed in December to enhance border security and maintain the flow of people and goods. ``With these two initiatives, we'll ensure faster movement of legal, low-risk goods and faster travel for people across our border, and we'll be able to better enhance security,'' Bush said. Iraq also loomed large on the agenda in Bush's sixth trip to Michigan, a state with a large trove of electoral votes that Bush lost in 2000. Bush and Chretien were almost certain to discuss the issue in a private meeting, though aides tried to keep the focus on border security and trade. Protesters held up signs that read ``Drop Bush, not bombs'' and ``No blood for oil'' as Bush arrived, and Iraq seemed to dominate the list of issues on the minds of those who traveled here to see the president. Dick Pierson came 25 miles from suburban New Baltimore to hear Bush and Chretien speak. Pierson, who owns a lumber and building wholesale company, said if he had a minute with Bush, he'd urge him to move cautiously before attacking Iraq. ``He needs to get the other countries behind him before he moves, just like his father did,'' said Pierson, referring to the Gulf War a decade ago. ``You've got to have consensus. You don't want to have the entire Arab world against you.'' Dan Stayer, a small business owner from the Detroit suburb of Rochester Hills, said he hoped Bush would thoroughly investigate a move on Iraq and work closely with his advisers before making a decision on the issue. ``Personally, I trust him,'' said Stayer, who was seated on a folding chair looking toward the Ambassador Bridge while awaiting the speeches by Bush and Chretien. ``Whatever he says, I'll back him up.''