The Bush administration, in a new security measure in the wake of the September 11 terror attacks, is imposing a 20-day waiting period for men from predominately Muslim countries who apply for visas to visit the United States.

Administration officials acknowledge the political sensitivity of singling out male applicants from largely Muslim countries for longer visa waits. But they say the new policy, likely to be in effect for several months, is a prudent measure to protect the United States' borders and people in light of the September suicide hijackings committed by 19 Arab men linked to the al-Qaida terror organization.

Starting next week, U.S. embassies and consulates in more than 20 Arab and other countries with large Muslim populations will require that male visa applicants between the ages of 16 and 45 wait 20 days while their names are sent to Washington for screening.

Until now, many visa applications from those countries were approved immediately after quick computer checks or granted within a few days.

The waiting period will allow U.S. officials to run the names and information provided by visa seekers through a computer database being upgraded to include information from U.S. intelligence agencies.

State Department officials say the waiting period will be dropped in a matter of months once the computer upgrade is completed and visa requests from around the world can be handled on a uniform basis.

In an interview with the Fox News Channel Friday Secretary of State Colin Powell said he was not aware of any early diplomatic protests over the visa policy and said he hopes affected governments will understand the need for the U.S. action. "We are sensitive to how it would affect some of our friends and allies around the world, and I hope they will understand that this temporary measure is needed for our security," he said. "And we will assure them, and reassure them, and again reassure them that the United States remains an open country. We welcome those who want to come to our country to visit, to go to school, to take a look around, for whatever purpose. We're that kind of a society."

But Mr. Powell also said that in "this time of tension and crisis," authorities have to know who is coming to the United States and have checked their identities through intelligence and law enforcement databases.

As part of the new policy, visa applicants will be asked to fill out a detailed form asking them about military service, weapons training, past travel, and whether they have ever lost a passport.

The visa plan is part of a broader tightening of U.S. immigration procedures since the September 11 events.

Most of the hijackers in the New York and Washington terror attacks were Saudi nationals, and while many had entered the United States legally, some had overstayed student visas or were otherwise in violation of U.S law.