For two years, European officials have wrestled with Greece to try to save the country from financial ruin. Yet the closer talks get to a definitive deal, the greater the risk seems to get that negotiations might collapse once and for all.

Deadlines have come and gone, as have rescue packages, but now there is a firm one. Greece will be unable to meet massive bond payments on March 20 without more aid.

A first, 110-billion-euro plan was put together in May 2010, only to prove insufficient as Greece's situation worsened. A second, 130-billion-euro deal was agreed last October, but is yet to be finalised despite drawn-out, high-pressure negotiations that have left nerves and tempers frayed.

So many moving parts now need to come together at a single moment to clinch the deal that the danger of one piece being out of place and scuppering the whole enterprise has never been greater.

They are dancing on a razor's edge, said Janis Emmanouilidis, a senior analyst at the European Policy Centre in Brussels who has written extensively on the debt crisis.

Time is now really, really short. The further the crisis develops, the more intense these moments become. If something goes wrong, and that's becoming increasingly possible, at some point it could all not work out, with whatever consequences.

Emmanouilidis, a German-speaking Greek who in that respect straddles the poles of Europe's debt debacle, thinks it will work out in the near-term, with Greece's political leaders reaching a last-minute accord with the EU and IMF.

The lenders have demanded all parties sign up to the austerity measures demanded as part of the second bailout but with elections approaching in April, that could be akin to writing a political suicide note.

Even if they do sign up, there are several other elements that could go wrong in a multifaceted conundrum that has been likened to playing three-dimensional chess but which sometimes now borders on quantum physics for its complexity.

The trend is that the situation is becoming more and more dangerous as the variables increase. The puzzle is becoming more complicated and the danger is bigger than ever before. But I still think things will fall into place, Emmanouilidis said.

DELICATE MACHINERY

For that to happen, at least six things have to come together between now and an EU leaders' summit on March 1 - the next putative deadline, although that could also be pushed back.

First, Greece's political parties need to agree that they are committed to a deal, which is no simple task given elections are due in April and every party leader is bidding for power.

Next the Greek government needs to submit a written commitment on the agreement to the European Commission, the European Central Bank and the International Monetary Fund, the 'troika' of overseers monitoring Greece's economic progress.

Then a deal that Athens has struck with private holders of Greek debt, which would see those creditors exchange around 200 billion euros of bonds for longer-dated securities with a lower coupon and half as much nominal value, has to hold - a sensitive process called a bond exchange that can take weeks.

At the same time, the troika must agree that the relief delivered by the bond exchange is sufficient to cut Greece's debts to 120 percent of GDP by 2020, from about 160 percent now - a stipulation the IMF is particularly firm on.

If that is not the case, then there may have to be a further negotiation over the official sector - the ECB and national euro zone central banks - possibly taking a writedown on some of their Greek bond holdings to bring the debt burden down further.

Euro zone finance ministers must sign off on all of that and launch the process of raising the funds Greece needs via the European Financial Stability Facility, their bailout fund.

And all of that must happen without parliamentary committees in Germany and Finland - which have to grant approval for their governments to commit - raising last-minute objections.

In all of those steps, analysts and officials see the greatest risk at the start of the process, with Greece's political parties, which were again in negotiations on Tuesday but have so far shown little inclination to bite the bullet.

The last mile has to be covered by the Greek political parties, the last mile to reach the second programme and to ensure a sustainable plan, said Amadeu Altafaj, the European Commission's spokesman on economic and monetary affairs.

We still hope for an agreement this afternoon at the meeting that Mr. Papademos will hold with the party leaders, he said, referring to the prime minister's last-ditch bid. But we are running out of time.

For Christoph Weil, a euro zone economist at Commerzbank, it is also Greece's politicians who have the ability to cut the Gordian knot, or else scuttle the EU's efforts, depending on how they respond to the troika's demands.

My base scenario is that there will be an agreement and we will see a second rescue package, so the problem will be under control for the moment, he said on Tuesday.

But in the longer run I am pessimistic, I think it is only a question of time before the Greeks leave the euro. Because they are unable to reform, the government is unable to reform its institutions at all.

Those feelings are reflected by others. It may be that Greek party leaders and the government deliver at the very last second and a debt default - failure to meet a 14.5 billion euro bond redemption on March 20 - is averted.

That, combined with the expectation that EU leaders will agree in March to increase the ceiling on their rescue fund to 750 billion euros, and that the ECB will deliver another shot in the arm to debt markets with more cheap three-year loans on Feb. 29, could shift the debt crisis onto a positive footing.

But still Greece's problems will linger. Already analysts expect Athens won't meet its commitments even if it signs up to them. That failure could be exposed at the first review, in theory due three months after the next programme is agreed.

The lack of confidence in Greece's ruling class has never been so high, said Emmanouilidis. There's this feeling that they can't deliver and also this sense that if they can't deliver, then the euro zone will have to do without them.

My feeling is that it will work out now, but if you look further ahead, beyond March... I don't know.