After the 9/11 terrorist attacks, Americans became rightly concerned about two serious issues — thwarting the international travel of terrorists and getting serious about enforcing U.S. immigration laws. Most of what was done immediately after 9/11 amounted to simply making it more difficult to travel to the United States from overseas.

Such caution was certainly understandable, but this approach isn't sustainable over the long term. International trade and travel benefit the United States enormously, accounting for more than a third of gross domestic product. America requires safeguards that will keep us safe, free and prosperous.

Congress seems to realize that a lot more can be done to make international travel both more secure and more free, and lawmakers have picked a good place to start doing both — with the visa waiver program.

Under it, the United States and 27 countries have agreements that permit citizens to travel among them for 90 days using their passports without getting a visa. The waiver program is a boom to tourism and business, bringing into the United States an estimated $75 billion to $100 billion a year. It also saves the U.S. government a lot of money and adds security, because it allows the State Department, which issues visas, to shift scarce resources to countries of concern.

The visa waiver program hasn't been expanded since 9/11 out of concern that terrorists, criminals or immigration violators might exploit the opportunity to travel here and remain unlawfully. But restricting casual travel with many countries that want stronger ties to America hampers our economy and diminishes our image abroad. Many countries want in to the waiver program. With that in mind, some senators have proposed enhancing its security provisions, as well as opening the potential for more of America's friends and allies to participate. It's a win-win proposal.

There are many reasons it's time to start thinking about strengthening and expanding the program. Friendly and allied countries worldwide are doing much more to thwart terrorist travel than they did before 9/11.

Every traveler who comes to the United States, even those in the waiver program, undergoes terrorist and criminal screening. International air travelers bound for the United States are checked against an integrated terrorist watch list. In addition, before they even depart for the United States, travelers already have been screened through the Advance Passenger Information System. Under it, all international inbound flights send a passenger manifest beforehand. Since October 2002, air and sea carriers under the visa waiver program submit both arrival and departure manifests electronically to the Department of Homeland Security for screening and analysis. According to the department, the passenger information system already has been used to uncover drug- and human-smuggling operations.

All countries hoping to participate in visa waivers have also agreed to implement an e-passport to prevent tampering and fraud. The e-passport includes fingerprints and a digital picture. In addition, the visa program requires travelers from participating countries to carry machine-readable passports, which make it easier to record and analyze travel data.

In addition, Homeland Security Secretary Michael Chertoff has proposed a number of enhancements for the waiver program. These include more routine sharing on passenger information, timely and accurate reporting on lost and stolen passports, and stronger agreements on repatriating illegal aliens, as well as cooperation in the federal Air Marshal program.

The Senate bill adds other security guarantees as well, including a mandatory exit check to ensure visitors depart. According to a study by the General Accountability Office, most visitors who illegally remain in the United States do not come from waiver-program countries. It's important to ensure that countries that want to enter the program don't abuse the system. The best way to do that is to ensure that travelers do not overstay. Requiring visa waiver travelers to use mandatory exit checks will provide rock-solid evidence of whether rules are being followed. Countries that do not measure up can be dropped from the program.

Expanding visa waivers would make America more secure and would strengthen the enforcement of U.S. immigration laws. The visa waiver program raises the bar for safe and secure international travel, and countries that are willing to participate will be committing to enforce higher standards, more vigilant security and stepped-up enforcement.

We can't win the war on terror by trying to seal America off from the rest of the world. Winning must include safe and open international travel for Americans and their friends and allies. Visa waiver program reform is the next step in the right direction.