The commissioner of the Immigration and Naturalization Service, whose agency has been severely criticized for a paperwork blunder involving student visas for two of the Sept. 11 hijackers, on Tuesday proposed tighter visa restrictions.

James Ziglar told a House Judiciary subcommittee that the student visa process had become lax because it was focused on serving students and the U.S. schools that accept them, but has been changed. He said he is considering several changes to visa rules, including:

— Reducing from six months to 30 days the time foreign visitors can remain in the country on a travel visa.

— Prohibiting visitors with travel or other visas from "gaming the system" by switching to a student visa. Any foreigner wanting to study in the United States would be required to state their intention before arriving in the country. Two of the hijackers, Mohammed Atta and Marwan Al-Shehhi, entered as visitors and had switched to student visas at the time of the attacks.

— Prohibiting foreigners from beginning their studies until their student visas are approved.

— Notifying schools electronically of approvals for student visas, and reducing the processing time for those applications to 30 days.

Ziglar said some of the rules could be put in place immediately.

The hearing came as President Bush's domestic security team recommended that the INS and Customs Service be merged to create a single border control agency, and less than two weeks after the INS delivered student visas for Atta and Al-Shehhi to a Florida flight school — six months after they flew hijacked jetliners into the World Trade Center.

Ziglar took some of the blame for the mistake.

"We should have known to go and pull [the paperwork] out," Ziglar told a House Judiciary subcommittee on immigration and claims.

Committee members chastised and grilled Ziglar for nearly two hours about that mistake and problems at INS. The belated delivery of visa approvals for the hijackers led at least one lawmaker to question Ziglar's credentials for the job.

"The complete lack of control and accountability of the INS illustrates so vividly the necessity for reorganizing the agency," said Rep. George Gekas, R-Pa., the subcommittee chairman. "While the INS blames the error of approving flight school training to two dead terrorists on outdated processes, the problem lies squarely on the shoulders of INS management."

Ziglar has undertaken an internal INS restructuring plan that had the administration's support. It would create clearer divisions between the INS' benefits and enforcement duties, but keep the agency intact. Some members of Congress want to abolish INS and create two separate agencies.