MADRID, Oct 11 (Reuters) - Spanish Prime Minister Mariano Rajoy on Wednesday took the first step towards activating article 155 of the Spanish constitution, a so-called nuclear option that would allow him to suspend Catalonia’s political autonomy and take over the region.

“The cabinet has agreed to require formally to the Catalan government to confirm whether it has declared or not independence,” Rajoy said in a televised address.

“The answer from the Catalan president will determine future events, in the next few days,” he also said, adding he would keep acting in a “cautious and responsible” way.

This formal requirement is needed to trigger the article 155 though the constitution does not establish any specific time frame for the answer. (Reporting by Julien Toyer; Editing by Paul Day)