New York City residents are still recovering from the attack on the World Trade Center and the recent plane crash over Queens. But that has not stopped Rep. Tom Tancredo (R‑Littleton) and other long-time critics of immigration from exploiting the Sept. 11 terrorist attacks to launch a war of another kind against our tradition of welcoming those who come here seeking the American dream.

In the wake of the Sept. 11 attacks on the World Trade Center and the Pentagon, Tancredo, leader of the Congressional Immigration Reform Caucus, introduced a bill that would impose a moratorium on new immigration. In a recent speech to the House that included a litany of complaints about the economic and cultural impact of immigration, Tancredo said, “Mr. Speaker, my God, what does it take? .… How many people in this country have to lose their lives before we come to the understanding that defense of the nation begins at the defense of our borders?”

As the former president of a think tank, Tancredo should know better: “Defending our borders” and drastically cutting immigration are two different propositions. The problem is not that we are letting too many people in but that the government is not effectively keeping the wrong people out.

Immigrants are only a small subset of the total number of foreigners who enter the United States every year. Only about 1 out of every 20 foreign nationals who enter the United States come here to immigrate. The rest are business travelers, students attending Colorado universities, tourists arriving for ski holidays, and Canadians and Mexicans crossing into border states for the weekend to shop or visit family.

The 19 terrorists who hijacked those planes did not apply to immigrate or to become U.S. citizens. Like most aliens who enter the United States, they were here on temporary visas. It’s disingenuous of Tancredo to aim his moratorium at the small share of aliens entering the United States who want to immigrate when terrorists are far more likely to enter through the much broader gates open for tourists and other visitors. We could reduce immigration to zero and still not stop terrorists from slipping into the country on temporary, non-immigrant visas.

Everyone can agree that we must do more to stop potentially dangerous people at the border. Law enforcement and intelligence agencies must work closely with the State Department, the Immigration and Naturalization Service and U.S. Customs to share timely information about potential terrorists. Computer systems must be upgraded and new technologies adopted to screen out the bad guys without causing intolerable delays at the border. More agents need to be posted at ports of entry to more thoroughly screen for high-risk travelers. We need even more cooperation from Mexico and Canada to prevent potential terrorists from slipping across our long land borders into the United States.

Just as importantly, America’s border control system requires a reorientation of mission. U.S. immigration policy up until now has been obsessed with nabbing mostly Mexican-born workers whose only “crime” is their desire to work, save, and build a better life for their families. Those workers pose no threat to national security. Instead of expending scarce resources to hunt down construction workers and raid restaurants, our border control efforts should focus on tracking potential terrorists and smashing their cells before they can blow up more buildings and kill more Americans.

Drastically reducing the number of foreigners who enter the United States each year — — the goal of Tancredo and other “restrictionists” — — would only compound the economic damage of Sept. 11 while doing nothing to enhance our security. Whole sectors of the U.S. economy depend on foreign-born workers, high- and low-skilled alike, from Silicon Valley and Wall Street to hotels, restaurants, construction sites and farms. The tourist industry, already reeling, would lose millions of foreign visitors and American universities would lose hundreds of thousands of foreign students if our borders were closed.

Like the Statue of Liberty, the World Trade Center towers stood as monuments to America’s openness to immigration. Hundreds of foreign-born workers from more than 80 different nations lost their lives in the terrorist attacks. To honor all victims of Sept. 11, the U.S. government must do more to apprehend terrorists while keeping our door open to peaceful, hard-working immigrants who come here to build a better life.

We should post a yield sign on the Statue of Liberty, but never a stop sign.