Spanish Prime Minister Mariano Rajoy says he won't rule out suspending Catalonia's regional autonomy if its leaders continue to threaten a declaration of independence.

"I don't rule out anything," Rajoy said in an interview in the daily El Pais Sunday when asked about applying the constitutional provision that allows the suspension.

"But I must do things at the proper time... I would like the threat of an independence referendum to be withdraw as quickly as possible," he added.