WASHINGTON — The U.S. State Department will begin revoking the passports of parents who owe $100,000 or more in unpaid child support on Friday, the start of an expanded enforcement program. The program will later be broadened to cover parents who owe more than $2,500, the threshold set by a 1996 law that has been little enforced.

About 2,700 American passport holders owe $100,000 or more in unpaid child support, according to figures supplied by the Department of Health and Human Services. It was not clear how many passport holders owe more than $2,500 in unpaid child support because the department is still collecting data from state agencies.

Until recently, only parents who applied to renew their passports were subject to revocation for unpaid child support. Under the new policy, the Department of Health and Human Services will inform the State Department of all past-due child support payments over $2,500, and parents in that group with passports will have their documents revoked.

"We are expanding a commonsense practice that has been proven effective at getting those who owe child support to pay their debt." Assistant Secretary of State for Consular Affairs Mora Namdar said. "Once these parents resolve their debts, they can once again enjoy the privilege of a U.S. passport." she said.

Since February 10, the department has seen data that hundreds of parents resolved their arrears with state authorities after the expansion was reported. The department said in a statement, "While we can't confirm the causation in all of those cases, we are taking this action precisely to impel these parents to do the right thing by their children and by U.S. law."

Since the passport revocation program began in earnest in 1998, states have collected $657 million in child support arrears, the department said. In the past five years, states have collected more than $156 million in over 24,000 individual lump-sum payments under the program.

Parents whose passports are revoked will be notified that they cannot use their documents for travel and must apply for a new passport once their arrears are confirmed as paid. Passport holders abroad at the time of revocation will need to visit a U.S. embassy or consulate to obtain an emergency travel document that allows them to return to the United States.