This comes as the State Department faces a massive backlog for new and renewed passports as foreign travel starts to open for Americans following a year and a half of COVID-19 restrictions.
The department's website said it disabled its booking system entirely to "ensure our very limited appointments go to applicants who need them for urgent travel."
Last week, department officials said the wait for a passport is now between 12 weeks and 18 weeks, even if you pay for expedited processing. That's because of ripple effects from the coronavirus pandemic that caused extreme disruptions to the process at domestic issuance facilities and overseas embassies and consulates.
With online appointments shut down, the State Department is only taking new applications by phone.
This way, a representative can instead give an applicant unique confirmation information used to verify that the person who made the appointment is the same person who comes in, a department official told ABC News. It's unclear why the department can't do that online.
Callers may need to wait for more than an hour to reach a representative before making an appointment, per the official.
"At the moment, demand is greater than supply, although we're adding more appointments as more staff return to our passport agencies," that official said.
In-person appointments are still extremely limited and prioritized for life-or-death emergencies, the official added.
Over the past week, the average daily number of travelers screened by the TSA has topped 2 million. A department official says a backlog of 1.5 million to 2 million passport requests means that applications submitted now probably will not be processed until the fall.
The Associated Press contributed to this report.