(AP) — Parents who owe a significant amount of child support soon could lose their ability to travel internationally as the Trump administration expands and steps up enforcement of a 30-year-old law that allows the federal government to revoke American passports until payments are made, three U.S. officials told The Associated Press.

While passport revocations for unpaid child support of more than $2,500 have been permitted under 1996 federal legislation, the State Department had in the past acted only when someone applied to renew their travel document or sought other consular services. In other words, enforcement depended on the person approaching the department for assistance.

Starting soon, however, the department will begin to revoke passports on its own initiative based on data shared with it by the Health and Human Services Department, according to the U.S. officials familiar with the plan. They spoke on condition of anonymity because the change has not yet been publicly announced.

The number of people who could be affected was not immediately clear, but it is believed to be in the thousands. Because of the potentially large universe of those owing child support who currently hold passports, the State Department will make the change in tiers, the officials said.

The first group to be affected will be passport holders who owe more than $100,000 in past-due child support, the officials said. One of the officials said fewer than 500 people meet that threshold and could avoid having their passport revoked if they enter into a payment plan with HHS after being notified of the pending revocation.

The official acknowledged, though, that if and when the threshold is lowered to a smaller past-due amount, the number of those affected will rise significantly. The official could not say when any further changes would take effect or estimate how many people might then lose their passports.

Since the Passport Denial Program began with the 1996 passage of the Personal Responsibility and Work Opportunity Reconciliation Act, the initiative has taken in nearly $621 million in past-due child support payments, with nine collections of more than $300,000, according to the Office of Child Support Enforcement at the Department of Health and Human Services.

HHS did not respond to questions about how many people are in arrears, instead referring the AP to the State Department. The State Department did not immediately respond to a query about the move.