Barcelona, Spain - If Spanish Prime Minister Mariano Rajoy persists "in preventing dialogue" and follows up on a threat to strip Catalonia of its autonomy, the Catalan parliament will declare independence, Catalan President Carles Puigdemont said.

Madrid is expected to respond to Puigdemont's latest letter, released on Thursday.

On October 10, Puigdemont declared independence for eight seconds before suspending the declaration to encourage talks with Madrid. Rajoy responded with an ultimatum, giving Puigdemont until Monday to clarify his stance.

On Monday, Puigdemont offered two months of dialogue with Madrid to foster independence. Madrid then extended the deadline to October 19, but threatened to invoke Article 155 of the Spanish Constitution, which would strip Catalonia of its autonomy.

Thursday's developments extend a struggle between Madrid and Barcelona over the status of Catalonia since the disputed October 1 referendum on secession from Spain, which was halted by "excessive force" from Spanish national police.

The Catalan government says voters overwhelmingly supported independence with 90 percent of votes for secession, but turnout was less than 50 percent.

Spanish and Catalan-language media reports say that Rajoy has convened a meeting of ministers to enact Article 155, which is described as the "nuclear option" and has never been used since the constitution was ratified in 1978.

Spanish authorities are reported to be unsure of its implementation.

The stripping of Catalonia's autonomy is sure to increase tensions between Madrid and Barcelona, which are already high. Two pro-independence organisers, Jordi Cuixart and Jordi Sanchez, were imprisoned Monday without bail pending charges of sedition.

An estimated 200,000 people took to the streets to demand their release in Barcelona on Tuesday, calling them "political prisoners."