Speaking in the Spanish Congress, Saenz de Santamaria said that the Catalan Regional Assembly "wanted to end with decades of democratic stability" in Spain.
The development came as US President Donald Trump and Spain's Prime Minister Mariano Rajoy told journalists they opposed the referendum in Spain's Catalonia region scheduled for Sunday.
The Spanish government has sent thousands of police officers to Catalonia in the run-up to Sunday's planned referendum.
With five days to go until the October 1 vote, the clash between Catalonia's pro-separatist government and Madrid is increasingly being played out in the arena of logistics and global opinion. Trump said. "I'm just for a united Spain", he said, adding that if accurate polling were done in the region "you'd find out people of Catalonia love their country, they love Spain".
Madrid has responded with the heavy legal artillery at its disposal to block the vote, dealing a blow to plans to hold a vote with a semblance of legitimacy. Catalonia's leaders retort they have a right to decide their future even if it not allowed by the Constitution.
Oliver Jones from Capital Economics said: "In Spain, a referendum on Catalan independence is set to occur on 1st October".
The remarks of the two US spokeswomen come as Spanish courts have declared the referendum mandating secession illegal.
Spanish security operations to thwart a controversial secession referendum in the northeastern region of Catalonia were continuing on Tuesday as online operations rendered over 140 pro-independence web pages inaccessible.
The Spanish prosecutor has previously warned that Catalan officials involved in the preparation of the referendum on independence could be charged with disobedience, abuse of power and embezzlement of public funds.
Many had not yet received information about where or when they would be working after the state-run postal service was told to stop all mail related to the vote, Marta Rovira said in a radio interview.
A vote to split could also encourage other areas to vote for independence from the European Union (EU), experts said.
Although Catalonia enjoys a certain measure of autonomy, separtists have long campaigned for independence for a wealthy region with its own language and cultural traditions.