Notre-Dame Cathedral's rector says the faithful might need to get used to not attending services for a long time -- or ever again -- after it was unable to host traditional Christmas services for the first time since the French Revolution.

Monsignor Patrick Chauvet told The Associated Press that restoration work on the famous Paris landmark isn't likely until 2021, saying there’s a “50 percent chance” the structure might not be saved.

“Today, it is not out of danger,” he said after a Christmas Eve midnight Mass held at a nearby church. “It will be out of danger when we take out the remaining scaffolding.”

NOTRE-DAME CATHEDRAL CAN'T CELEBRATE CHRISTMAS MASS FOR FIRST TIME IN 200 YEARS FOLLOWING DEVASTING FIRE

He added: “Today we can say that there is maybe a 50 percent chance it will be saved. There is also a 50 percent chance of scaffolding falling onto the three vaults, so as you can see the building is still very fragile.”

The 12-century cathedral was under renovation when a massive blaze broke out in April, destroying its roof and collapsing its spire. Without a roof to keep the massive stone structure stable, the cathedral’s surviving vaults are crucial, but they are vulnerable.

Some 50,000 tubes of scaffolding crisscrossed the back of the cathedral at the time of the fire. Removing them without causing further problems is one of the toughest parts of the cleanup.

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“We need to remove completely the scaffolding in order to make the building safe, so in 2021 we will probably start the restoration of the cathedral,” Chauvet said. “Once the scaffolding is removed we need to assess the state of the cathedral, the quantity of stones to be removed and replaced.”

Chauvet estimated it would take another three years after that before the cathedral is safe enough for people to re-enter. President Emmanuel Macron has vowed to rebuild it by 2024, the year that Paris will host the Olympics.

Experts have called that time frame unrealistic.

Tourists can photograph it from nearby embankments, but they can no longer hear its organs or get a close view of its carvings and masterpiece rose windows. The vast forecourt is barricaded, barren of its Christmas tree.

The Associated Press contributed to this report.