Spain gears up for bank bailout by eurozone partners
Up to 60bn euros (£48bn; $78bn) will be needed to bail out Spain's banks, according to the country's second biggest lender, BBVA.
The results of independent stress tests of the Spanish banking sector will be published on 28 September.
But previews are already being sent to the country's financial institutions.
The BBC has been told that the Spanish government has already put in place economic reform plans that would allow it to apply for a bailout immediately.
Spain's conservative Prime Minister Mariano Rajoy has in the past insisted Madrid would not become the fourth European capital in recent years to apply for such a bailout, but sources indicate such a programme is now likely.
Spain's banking sector needs recapitalising, and much of the money would come from 100bn euros in European Union funds already pledged by eurozone finance ministers in June.
"We'll get a figure of around 70, 75 or 80 billion euros," BBVA's Chairman Francisco Gonzalez said.
That figure includes around 20bn euros already allocated to troubled banks, which means 50-60bn euros is still required.
The bigger question however for investors is how the Spanish government begins to balance its books.
Wider rescue plan?
Many in Brussels and beyond now assume it is only a matter of time before Spain becomes the fourth eurozone country to take a bailout.
A source in Brussels said the preference is that Madrid applies for the money sooner rather than later, before market conditions change.
That is important because of the different manner in which this bailout is being put together. A European Commission spokesman said it would be wrong to see this as a "kind of proto-bailout" - but to many it does look like a bailout-by-stealth.
Over the last few months Spanish officials have held numerous meetings with their European counterparts, working out what Madrid would have to do to fulfil the criteria of any bailout deal.
Officials say Spain is already living up to any future bailout terms.
Next Thursday Mr Rajoy will unveil the next Spanish budget. Rather than more cuts, more austerity, he is pushing for structural reforms to help him make savings.
Such reforms will form the basis of a bailout agreement with the so-called troika - the European Commission, European Central Bank and International Monetary Fund.
For a programme to work, all that would need to be added would be firm dates for implementing such reforms and a team to monitor progress.
Asked to comment, the Spanish finance ministry did not deny that negotiations to this effect had taken place.
It could give Spain's prime minister enough wiggle room to present this to his country as a Spanish-led process.
Many will not believe him, but it helps a leader who said he would never apply for a bailout to save some face.
The hope is also that Spain - unlike Greece, the Republic of Ireland and Portugal before it - will not be locked out of the bond markets.
It will still be able to borrow from investors. There will be less of a loss of sovereignty for Madrid than there was for Athens, Dublin and Lisbon.
Timings on a possible bailout however are unclear. Following the ECB's promise to support countries like Spain that find themselves having to pay record levels to borrow from investors, the market pressure on Madrid has reduced substantially.
As one diplomat in Brussels suggested, that may have pushed away the immediate need for a bailout.
Countries like France though are keen for the eurozone to "get ahead of the crisis" - and bailing out Spain now would be a way to do that.