Greece’s metaphoric D-Day has come and passed. For months, May 19 has loomed as Greece’s day of reckoning due to uncertainty about Athens’ ability to come up with the 8.5 billion euros ($10.8 billion) needed to repay a maturing 10-year bond. But with a 14.5 billion-euro tranche of the 80 billion-euro rescue package arriving May 18, Greece has enough to repay the bond and more. German state bank KfW contributed more than 4.4 billion euros while France contributed more than 3.3 billion euros. Greece also received a 5.5 billion-euro tranche of its 30 billion-euro International Monetary Fund (IMF) package, bringing Athens’ total new funds to 20 billion euros.

While the capital injections will allow Greece to avoid tapping commercial markets for lending during 2010, Athens is by no means out of the woods. It must still prove its commitment to austerity measures or it could lose access to the bailout funds.

The combined 20 billion-euro injection came just in time for Greece. After May 19, Athens needs to muster another 6.8 billion euros for additional maturing debts, most of which is due in July and then in October. It also will have a 14 billion-euro budget deficit to patch up — assuming its deficit does not widen further — and will need about 7.5 billion euros to cover interest payments on existing debt. This means that after the initial 20 billion euros are spent, Athens will need at least another 16.8 billion euros to get through the remainder of 2010.

And this is why EU and IMF monitoring of Greek austerity measures now becomes crucial. Greece is supposed to receive another 18 billion euros in EU and IMF funds in September — just enough to finance its remaining outlays — but the transfer will be contingent on a successful June evaluation. A mission from the European Central Bank (ECB), the EU Commission and the IMF will visit Athens in June and publish a progress report in July.

Whether Athens can sustain its budget austerity measures in light of intense union protests remains to be seen. Greek public sector unions are set to stage their fourth general strike of this year on May 20. Furthermore, it appears the possibility of ongoing unrest could prompt large numbers of tourists from Western Europe to cancel their summer vacations to Greece. As tourism accounts for 18 percent of Greek gross domestic product, such cancellations would only further aggravate the Greek and economy and Athens’ budget deficit.

Finally, Greece is staring at a further 27.7 billion euros of debt maturing in 2011, 30.8 billion euros in 2012, 24.6 billion euros in 2013 and 31.3 billion euros in 2013. However, as the Greek economy continues to reel from the imposed austerity measures, Athens may need to take on even more debt at a time when its ability to repay continues to deteriorate. The 110 billion-euro bailout therefore (literally) buys Athens time to rationalize its finances by improving tax collection and reducing public outlays, but to be successful, Athens must also manage the public outrage over the austerity measures.