MADRID, Spain (PNN) - May 24, 2012 - Ángel de la Peña, a Spanish government worker, is seriously considering the once unthinkable: converting some of his savings from euros to British pounds.

It is only a trickle so far, and not nearly enough to constitute a classic bank run. But these growing transfers of deposits out of troubled Spanish banks reflect a broader fear that the country’s problems could make it hard for Spaniards to get to their money if banks fail and cannot be supported by the government.

Money already has been pouring out of banks in Greece, where many citizens believe it is increasingly likely that their country will be forced to leave the euro zone. But for European policy makers and economists, the possibility of mini-runs on banks spreading from Greece to other, bigger countries like Spain - with 1 trillion euros, or $1.25 trillion, in bank deposits - poses a much more serious risk.

Indeed, the outflow of money from Spanish banks could increase if the ratings agency Standard & Poor’s, as expected, downgrades Spanish banks, in effect saying that their weakened state makes them riskier.

In Greece, more than two years into its financial crisis, nearly one-third of the country’s bank deposits have already left the country.

So far, there has been no such exodus in Spain, where over the last year about 4.3% of bank deposits, or 41 billion euros, the equivalent of about $51 billion, has been transferred out of the country. But that amount is in addition to a decline of 140 billion euros in foreign-owned financial assets in the last year, like the sale by foreigners of Spanish government bonds.

What is more, the condition of Spanish banks is expected to worsen over the next year, as commercial real estate and mortgage losses - a big source of the nation’s bank troubles - continue to mount.

At their essence, bank runs are fear-driven phenomena. Once they start, they are difficult to stem.