Spain's government has secured support from top world leaders as it resists Catalan separatists' vows to break away within 18 months if they win Sunday's regional election.
Catalonia's leader regional president Artur Mas shrugged that off as "all part of the game" of international relations between Spain and its allies.
Mas's foreign affairs secretary Roger Albinyana said Madrid must be on the defensive if it "feels the need to make the conflict international".
Meanwhile, Mas and his Catalan nationalist allies are waging their own diplomatic campaign for support in power centres such as Brussels and Washington.
Obama urges 'unity'
Spain's Prime Minister Mariano Rajoy was credited with a coup last week after US President Barack Obama tacitly weighed in against the independence camp, calling for "a strong and unified Spain".
Spain is a key strategic ally of the United States, which has thousands of troops stationed on Spanish soil, handy for missions to the Middle East and North Africa.
Before Obama's comment, British Prime Minister David Cameron warned Catalonia it would drop out of the European Union if it left Spain.
He took the same stance against independence for Catalonia as he had on Scotland, which a year ago voted against independence in a referendum he authorised.
Before Cameron, German Chancellor Angela Merkel stood alongside Rajoy and voiced her support for the "integrity of Spain".
Rajoy is an economic ally of Merkel, having pushed through tough austerity reforms with her encouragement. Her comments came at a meeting at which Rajoy committed to accepting more refugees.
France's leaders have not taken a public stance recently on Catalonia. But its former president Nicolas Sarkozy is scheduled to join Rajoy at an anti-independence electoral rally in Catalonia on Friday, the Spanish premier's Popular Party said.
While Rajoy has garnered the backing of big world allies, Mas's camp has sent delegations to various national parliaments and to Washington for meetings with US congressmen.
At least one of those, Dana Rohrabacher of California, spoke out publicly this month in favour of Catalan self-determination.
Mas's government has a network of "diplomatic offices" abroad and recently opened new ones in Austria and Italy.
It has named a permanent representative to the European Union and has written to foreign embassies defending its independence plan.
But its efforts have so far yielded few high-profile endorsements.
No foreign powers have said they would recognise a Catalan republic.
But Albinyana insisted "there are certain countries in Europe and beyond that are sympathetic to the notion of its independence."
Living without EU
The European Commission has warned Catalonia, as it did Scotland, that it would cease to be in the EU if it left Spain - but Mas says that is not a sure thing.
Albinyana said "no EU country" would want such a rich, strategically located land to leave the bloc. If Catalonia did leave, he said, "a mechanism would be activated to keep it in".
"That is a fiction," said Ignasi Guardans, a former member of the European parliament and an estranged former ally of Mas. "It is a leap of faith that makes no sense."
If Europe accepted Catalonia's secession, that could set a precedent for "other countries with territorial crises", Guardans said - such as Flanders in Belgium or Venice in Italy.
By Daniel Bosque