Four advocacy organizations representing thousands of colleges and universities sent a letter to U.S. Secretary of State Colin Powell this week asking that he postpone the State Department's requirement that nearly all international visitors to the United States undergo an in-person interview before they get their travel visas.

College officials are afraid that the new mandate will lead to increased delays that will keep students and scholars from arriving on campuses in time for the fall term. They fear that that, in turn, will discourage foreign students and scholars from coming to American institutions to study, teach, and do research.

"If the system is backed up interminably, we're not aware of what we can do to compensate," said Martin C. Jischke, president of Purdue University.

The presidents of the Association of American Universities, the American Council on Education, the National Association of State Universities and Land-Grant Colleges, and the Council of Graduate Schools signed the letter. (The full text of the letter is available on the council's Web site. It can be viewed using Adobe Reader, available free.)

The new regulation is part of the department's cooperation with the White House and the Department of Homeland Security to scrutinize foreign visitors more closely and weed out potential terrorists. One tactic in that effort is to increase the number of visa applicants who are interviewed.

Mr. Powell announced the regulation last month in a message to American embassies and consular offices. The secretary made it clear then that he knew delays would occur. At some diplomatic posts, "the new regulations will result in a significant increase in the percentage of applicants interviewed," the message reads. "The Bureau of Consular Affairs will work closely with those posts to try to provide the resources necessary to cope with any additional workload, but expects and accepts that many posts will face processing backlogs for the indefinite future."

In their letter to Mr. Powell, the presidents of the four higher-education groups suggested that the State Department should delay the interview requirement until sufficient resources can be devoted to the task. They also suggested that the department phase in the requirement, based upon the students' country and their potential security risk.

There is already some evidence that the policy is starting to hinder foreign students' ability to arrive on time for the fall term. The letter mentions a student from India admitted to Purdue University who was informed by a State Department consular office in India that the earliest he could schedule his interview would be August 21. Purdue's fall term starts on August 25.

Given the interview backlog that already exists, it's not certain whether the student will be seen on that earliest-possible date, said Mr. Jischke, the university's president. Even if he is, he said, he would have only a few days to make his arrangements to travel.

Foreigners who do not make it to campuses on time face certain risks, said Michael A. Brzezinski, director of the office of international students and scholars at Purdue. Depending on the institution and the academic department that accepts them, he said, graduate students must arrive before classes start to secure their teaching and research assistantships. Undergraduate students who miss more than one week of class have a difficult time catching up.

"In some ways," Mr. Brzezinski said, "it's arrive on time or defer your admission to another semester."

May, June, and July are key months for visa applicants, Mr. Brzezinski said. He said he hopes the interview deadline will be pushed back to allow colleges to get through their preparations for the fall term.

The difficulty international students have in getting American visas is starting to lower foreign enrollment at U.S. institutions, Mr. Jischke said. His university has seen a 10-percent drop in applications from international graduate students, he said, and "it's hard to explain it by factors other than the difficulty in getting a visa."

Mr. Brzezinski said that two countries -- Malaysia and Saudi Arabia -- are already directing their citizens not to study in the United States.