Fears that Greek businesses may be unable to pay their euro-denominated debts intensified Thursday, when two big companies that sell policies to cover exporters against losses from businesses that don't pay their bills said they will stop insuring Greek transactions. 

The announcement signals increasing difficulties for Greek businesses to get trade credit, which is necessary to import goods and thus keep the nation's economy running, and is one of the latest -- and most dangerous -- developments in the country's chronic financial crisis.

The situation is growing so dire, analysts have begun to wonder how exactly Greece will be able to keep the lights on if the current crisis and, more specifically, speculation about the country exiting the common euro currency union, keeps going on for much longer.

People offering trade credit to Greece have been skittish in recent weeks as talks have intensified regarding a potential exit from the euro zone. The fear is Greece will exit the euro in the next few weeks, before payment on recently delivered goods and services is due. In such a scenario, Greek companies and government entities, which will likely be stuck reverting to a rapidly devaluing currency, might have trouble making payments in euros.

When credit stops, trade stops. And when trade stops, a steep drop-off in the standard of living, and resulting sociopolitical repercussions, can ensue. There is no country in the world that currently has the ability to keep its citizens clothed, fed, warm and enjoying the lifestyle they are generally used to without trade.

Keeping the heat and lights on is particularly problematic without the ability to exchange goods on credit, and appears to be the first place where the seams of international trade are coming apart for Greece.

For most of 2011 and 2012, as the rest of the world began shunning commerce with the country in a politically motivated embargo, Iran provided oil to Greece on generous credit terms. But Iranian state media reported in April that Iran was cutting off shipments to the Hellenic Republic on account of non-payment.

Since then, other countries have stepped up to provide Greece with energy commodities on a tab, but apparently only the most risk-loving companies within those nations are taking the lead. As a commodities trader recently told The Wall Street Journal, most market participants were completely reluctant to deal with Greece.

Two giant companies that have kept the oil import financing have been Dutch Vitol Group and Swiss Glencore International PLC, the world's No.1 and 2 oil traders, which trading sources told Reuters had extended about €300 million euros ($375 million) in open credit financing since April.

But the action has been no charity on the part of these international giants, who are charging hefty premiums on the interest rate Greece must eventually pay them back. Citing traders, Reuters estimates the premium could be as much as 50 cents a barrel or more, which would result in an additional payment of at least $2.2 million per month.

Indeed, paying a risk premium to traders and financiers with enough of an appetite to deal with the country appears to be the way Greece has also kept the flow of other goods coming in. But the prospect for doing that indefinitely changed dramatically Thursday.

Euler Hermes and Coface, two of the world's biggest credit insurers, said Thursday they would stop doing just that.

The conundrum now faced by trading partners was neatly summarized by Kostis Michalos, chairman of the Athens Chamber of Commerce, who was quoted in the Financial Times as stating the choices were now find an alternative insurer and pay through the nose, or simply take the risk themselves -- which is what some companies will do.

Those options, of course, are meant to keep trade going. A darker possibility is that firms reliant on imports will simply shut down. Already, Greece has seen one in five retail outlets selling imported goods close over the past two years

 We see that goods are already missing from supermarket shelves as the situation has worsened, Michalos told the Financial Times.

With Euler Hermes and Coface no longer offering policies on Greek imports, it's only bound to get worse.