Shares in Spain's fourth-biggest lender Bankia SA have been suspended on the Madrid stock exchange today.
This comes ahead of an evening announcement when the bank is expected to ask the state for a rescue of more than €15 billion.
The government is in the process of nationalising Bankia, which holds some 10% of the country's bank deposits.
It was unable to raise enough capital to cover heavy losses from loans to property developers during a building boom that crashed in 2007-2008.
Bankia and other banks exposed to the property bust are seen as a major risk for Spain and for the entire euro currency zone, because of concerns that the government will end up having to ask for international aid to prop up lenders.
Earlier this week Economy Minister Luis de Guindos told a congressional committee that the state would have to put at least €9 billion into Bankia to cover losses on sour loans and repossessed housing.
The government has already spent €4.5 billion to prop up Bankia and the entire rescue is now seen totalling some €20 billion.
The figure has risen several times in recent months. Some weeks ago de Guindos pledged that no public money would be put into the banks.
Spain will have to go to the markets to raise debt to put into Bankia, at a time when its borrowing costs are high.
Spain's country risk, as measured by the spread between benchmark German and Spanish bond yields, jumped as high as 500 basis points in recent weeks.
Today it had moderated to 462 basis points as investors moved out of German debt to hunt for higher yields.