Spain's ongoing dispute with Catalonia could come to a climax with speculation that the region's president might make a unilateral declaration of independence as early as this evening.

Carles Puigdemont is due to address the regional parliament in Barcelona on Tuesday, drawing warnings from the Spanish central government that it will not allow the country to be split.

The speech was originally scheduled for 16:00 GMT, but later delayed by about an hour, according to local media.

"Spain is not going to divide and national unity will be maintained. To do so, we will use all of the instruments that the legislation gives us. It falls to the government to take the decision and to do so at the right time," Spanish Prime Minister Mariano Rajoy told Spanish newspaper, El Pais.

Deputy Prime Minister Soraya Saenz de Santamaria said Spanish leaders were considering "all possible options" and described the Catalan leader's push for independence as "fanaticism".

"We are ready for any circumstances because we are already vaccinated against the fanaticism of Mr Puigdemont and any hope that he will return to sanity and serenity," she said.

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Rajoy's centre-right People's Party has the backing of the opposition Socialists, who have promised to back the government should Catalonia attempt to break away.

The Catalans held an independence referendum on October 1 and secured a 92 percent vote in favour of separating from Spain.

However, a unionist boycott of the vote meant turnout stood at just 43 percent.

Spain's government tried to block that vote by force and faced criticism when images of police officers confiscating ballot boxes and dragging voters away from polling stations were broadcast globally.

Madrid has the backing of Spain's courts, which ruled last week to block Tuesday's gathering of the Catalan parliament.

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The Spanish monarch, King Felipe VI, has also called on the government to maintain the "constitutional order".

Puigdemont has dismissed criticism from both the monarchy and central government and vowed the regional parliament will show the "best face to apply the results of the referendum".

A declaration of independence might take a symbolic form to allow space for negotiations with Spain.

The pro-independence Catalan National Assembly has said it will set up large screens outside the Catalan parliament to follow Tuesday's proceedings.