Catalan separatist parties say their victory in regional elections on Sunday gives them a mandate to push for independence from Spain.
The Madrid government has reaffirmed its opposition to a vote on secession, noting that nationalists failed to get a majority of Catalonia's popular vote.
The main separatist alliance and a small pro-independence party won 72 of the 135 regional parliament seats.
Despite their parliamentary majority, separatists got 47.8% of votes cast.
Catalonia has 7.5 million people and provides about one-fifth of Spain's national output (GDP).
'Yes to independence'
"Catalans have voted yes to independence," Catalan regional President Artur Mas told cheering supporters.
"We have a clear, absolute majority in the Catalan parliament to go ahead," Mr Mas added.
His "Junts pel Si" (Together For Yes) coalition has vowed to implement a "roadmap" to achieve an independent Catalan state within 18 months.
The future of Catalonia is expected to be a crucial issue in Spain's general election in December.
The turnout of 78% was a record for a regional vote in Catalonia.
A spokesman for Spain's ruling conservatives, the Popular Party (PP), argued that the separatists had "failed" by not securing a majority of votes.
The PP's Pablo Casado said "this election should serve to end the independence debate once and for all".
Junts pel Si won 62 seats. It can secure a parliamentary majority by combining with the far-left separatist CUP party, which got 10 seats.
Pro-independence Catalans argue that their region gets an unfair deal, contributing too much tax to Madrid in return for insufficient state investment. In terms of GDP theirs is the richest region in Spain.