Congress has agreed to fund a controversial administration program under which male visitors from Muslim countries are registered and fingerprinted, but is demanding a detailed explanation of the program's origins, its efficacy and the reasons for a large number of resulting detentions.

The registration program has stirred fears of deportation among visiting foreign nationals across the country and sharp criticism from Democrats in Congress, who say it has led to a wave of apparently unjustified arrests and incarcerations, especially in California.

Justice Department officials have defended the program, saying it has already proven successful in apprehending people who would have posed a risk to the public. Justice Department spokesman Mark Corallo said more than 400 "known criminals" and seven "known terrorists" have been taken into custody as a result of the new system.

The administration had asked for $362 million to cover the costs of the special registration system for the fiscal year that began last Oct. 1. The program is administered by the Immigration and Naturalization Service and will soon be transferred, with INS, to the new Homeland Security Department. The INS says it is needed to track the 35 million non-immigrants who come to the United States each year as well as "some non-immigrants already in the U.S."

Called the National Security Entry-Exit Registration System (NSEERS), the system imposed several requirements, including periodic in-person interviews at INS offices and check-ins with INS officers at specially designated exit points upon leaving the country.

The most controversial aspect of NSEERS is its application to males older than 16 from 25 countries, most of them predominantly Muslim, who were already in the United States last Sept. 30. The requirement caused widespread fear and confusion among foreign nationals, and hundreds suspected of immigration violations were at least temporarily detained.

Pakistan's foreign minister warned on a visit here two weeks ago that the requirement would bolster the cause of radical extremists there if it results in widespread deportations.

On Friday, the Justice Department announced it had extended the deadline for visa-holders from seven countries, including Pakistan and Saudi Arabia, to register.

The Senate last month refused to appropriate any money for the NSEERS and called instead for development of an automated system to track visitors at ports of entry. The administration called the denial of funds unacceptable.

House-Senate conferees handling the omnibus appropriations bill approved late Thursday agreed to provide the entire $362 million, on the condition that the Department of Homeland Security develop a plan to replace the INS's "current paper-based system and stovepiped databases."

At the same time, the conferees required delivery by March 1 of a large number of documents on the program to the Senate and House Appropriations committees. Among them are documents that assess the program's effectiveness "as a tool to enhance national security" and explain why some people with pending applications for green cards were detained.

Senate Democrats cited one report about a businessman from Iran who was arrested and jailed even though he has had a permanent resident application pending with the INS for five years.

Corallo said he was not familiar with the businessman's case, but that "most of the people with pending applications were held just for national security checks and released fairly quickly." Although exceptions can be made, he said, "we do not have the luxury any more of letting people go free while we do the check."