Top U.S. law enforcement officials are moving ahead with a broad tightening of immigration policy in the wake of the September 11 terrorist attacks.

Attorney General John Ashcroft says membership in, or support for, any one of 46 designated terrorist groups will result in immigrants being denied entry into the United States. "We will arrest and detain any suspected terrorist who has violated the law," said Mr. Ashcroft. "If suspects are found not to have links to terrorism or not to have violated the law, they will be released. But terrorists who are in violation of the law will be convicted, in some cases deported and in all cases be prevented from doing further harm to Americans."

Mr. Ashcroft made the announcement at a Washington news conference Wednesday, as he released details of a new foreign terrorist tracking task force aimed at improving coordination among U.S. agencies who monitor immigration.

As part of the crackdown on suspected terrorists seeking to enter the United States, Mr. Ashcroft says new background checks may be required for those wishing to obtain non-immigrant visas. "First, it will serve to elicit additional biographical and other information that is relevant to our security review," he said. "And second, it will serve to provide additional information that the FBI, INS and CIA can use as starting point to conduct further investigations before visas are issued."

But government officials readily acknowledge that they have a long way to go in improving coordination when looking for suspected terrorists who apply for visas.

Secretary of State Colin Powell addressed the issue at the State Department. "We want to make sure that every derogatory piece of information, every person who should not be allowed in the country or whom we have some information on that would suggest we ought to take a harder look at allowing that person into the country, when the name is entered, it pops up in the data base and gives the warning to our consular officers," he said.

The 46 groups designated by the attorney general include those affiliated with Osama bin Laden's al-Qaida network and other groups that U.S. officials have determined engage in terrorist activities.