The U.S. Embassy in Saudi Arabia made no secret that it prized convenience for travelers who sought visas to visit America.

"Applicants will no longer have to take time off from work, no longer have to wait in long lines under the hot sun and in crowded waiting rooms, and no longer be limited by any time constraints," U.S. consular officials in the kingdom announced in June, introducing an "express" visa program under which Saudis and others could send their requests to certain travel agencies, which became go-betweens with the U.S. Embassy.

Three of the Sept. 11 terrorists, it turns out, may have been among the first to benefit from the program, availing themselves of the service in the diplomatic and financial capital of Jidda in mid-June.

"Consular officers do not necessarily think of themselves as the front guard in border security," said Jessica Vaughan, a former U.S. Foreign Service officer in Belgium and Trinidad and Tobago, who has been critical of U.S. visa policies. "But they should, because they are."

In the aftermath of the terrorist attacks on the World Trade Center and the Pentagon, the once-obscure bureaucratic function of passing out visas has emerged near the center of debate concerning homeland security. Foreign Service officials and members of Congress argue that criminals find it too easy to get a U.S. travel visa--not just in Saudi Arabia but in many parts of the world. Consular employees, who make the decisions, may contend with a crushing load of requests in an environment that lauds "customer service" and seeks to project a positive U.S. image in the world.

On top of that, some question whether the State Department is more likely to reject the foreigner of limited means, who may be tempted to become an illegal immigrant, than the well-heeled, sophisticated traveler who may be a terrorist or member of organized crime. Under federal law, consular officials are supposed to watch out for foreign visitors who may be planning to stay permanently, a provision that focuses scrutiny on the poor.

"Visa policy has been oriented to keeping out the economic migrants, the tired, the poor, the huddled masses," said E. Wayne Merry, who retired in 1998 after 26 years in the Foreign Service, including a stint as head of the consular section in Moscow.

For citizens of most countries, the first step toward a visit to the United States is obtaining a visa from the local U.S. consulate. The usual two-page form asks for basic personal data, along with information about the length of the visit, who is paying for the trip and its purpose. Applicants are asked an array of questions, such as if they belong to a terrorist organization, have ever been arrested, refused entry to the United States or "participated in genocide."

Overall, U.S. officials approve three out of four applicants, and the totals are rising: The United States granted 7.7 million visas to visit the country for the year ended Sept. 30, a record, according to preliminary State Department figures, and a leap of 1 million from fiscal 1999.

Although a U.S. immigration official makes the final ruling about whether a traveler may enter the country, the visa decision "is absolutely crucial," said Doris Meissner, former commissioner of the Immigration and Naturalization Service and now a scholar at the Carnegie Endowment for International Peace. "It's the front line, it's the first, best chance that we have to respond effectively" when a criminal seeks entry into the United States.

Each of the 19 Sept. 11 hijackers entered the United States on valid visas, 15 from Saudi Arabia. Of those 15, four obtained their U.S. visas in Jidda in June, when the visa express program began, U.S. sources said. According to the newsmagazine U.S. News & World Report, three of the terrorists used the visa express program.

The State Department's electronic "lookout" database, which includes 5.7 million names, did not flag any of the terrorists.

State Department officials defend their system and are quick to point out that it is not possible for a consular officer to issue a visa unless the name has been checked in the lookout database. But all agree that the tool is only as good as the information fed into it.

"We have had a struggle with the law enforcement and intelligence communities in getting information," Mary A. Ryan, assistant secretary of State for consular affairs, testified in mid-October. As a result, she said of the hijackers, "they applied for visas . . . and their stories were believed."

The task of processing visas often goes to junior officers who are eager to shift over to the department's diplomatic and political fields.

"In my opinion, there has to be a much greater specialization within the State Department on visa issues if we believe the State Department should continue to have this function," Meissner said. "Using your beginning recruits and having them begin their first assignment [handling visas] and then go on to other things is just not very adequate to the task anymore."

Nikolai Wenzel, who served as a consular officer at the U.S. Embassy in Mexico City in the late 1990s, said he often handled 150 interviews in a single morning. In the afternoon, he would switch over to visa paperwork. His performance evaluation, he said, emphasized such things as his speed and politeness to applicants. "That was really the emphasis, rather than clear-cut enforcement of the law. . . . Overall, the reward was for moving the people through, cutting the lines down."

Wenzel, who works for a Washington think tank, maintains that the very fact that perhaps half of an estimated 7 million undocumented immigrants in the United States arrived here on legitimate visas is proof that visas often are allocated when they should not be.

Visa work, he contended in an interview, is "a hazing process, an unpleasant right of passage which a lot of officers don't take seriously."