The German parliament will hold a crucial vote today on whether to approve an extension of powers for the eurozone's financial rescue fund.

The Bundestag is expected to pass the legislation, backed by the opposition Social Democrats and the Green party – but the German Chancellor, Angela Merkel, is still struggling to persuade her own ruling coalition to vote in favour. If she is unable to win the support of her Christian Democrat party and their coalition partners, the Free Democrats, Ms Merkel would be expected to hold a parliamentary vote of confidence in her government. The expectation is she would lose such a vote, which would mean early elections.

The Chancellor can afford no more than 19 of her coalition MPs to rebel if she is to carry the vote in her own right. In a trial vote earlier this week 11 members of Ms Merkel's party rejected the legislation. And between two and five Free Democrat members are expected to do the same, which emphasises just how close today's vote is expected to be for the Chancellor.

Meanwhile, the "Troika" – a delegation from the European Commission, the European Central Bank and the International Monetary Fund – will return to Athens to decide whether the Greek government has made sufficient progress in sorting out its public finances to justify the release of the latest €8bn (£7bn) tranche of EU/IMF bailout funds. The return of the Troika has been interpreted as a sign that the funds will be forthcoming, but the group will not make a final decision on whether to release the loans, which Athens needs to avoid national bankruptcy, until next month.

Financial markets have perked up in recent days in response to talk of a grand plan to increase the powers of the stability fund, but investors were rattled yesterday by reports of a division among European policymakers over the scale of the write-downs that should be imposed on Greek creditors.

Eurozone leaders agreed in July that the holders of €340bn of Greek bonds should accept a 21 per cent "haircut" as part of the agreed second bailout for Greece. But now some German politicians are reported to be pushing behind the scenes for a larger writedown to be imposed on Greek creditors. This is being resisted by the French government and the ECB, who fear that reopening July's deal would further destabilise financial markets. French and German banks, which hold around €20bn worth of Greek bonds, would be particularly hard hit by a more extensive writedown.

The head of the European Commission, José Manuel Barroso, told the European Parliament yesterday that the EU is facing the "greatest challenge" in its history in the debt crisis, and urged the ECB to recognise its responsibility to prevent the break-up of the eurozone. He said: "We trust that the European Central Bank will do whatever is necessary to ensure the integrity of the euro area and to ensure its financial stability."

The mooted plan involves the ECB lending money to the €440bn eurozone stability fund, extending its firepower by up to four times.

Mr Barrosso also backed a financial transaction tax which he said would raise €55bn a year, arguing that the European financial sector must "make a contribution" in the fight to save the eurozone, and reiterated his support for a eurobond. "Once the euro area is fully equipped with the instruments necessary to ensure both integration and discipline, the issuance of joint debt will be seen as a natural and advantageous step for all," he said.

A hard road ahead: major obstacles still to be overcome

Hurdle 1: Bundestag vote on second Greek bailout

Today's vote is only Part One of the process of securing German parliamentary approval for the eurozone rescue efforts. Next month, German lawmakers will vote on the second Greek bailout, worth €109bn (£94.92bn), agreed by European leaders in Brussels in July. Then the Bundestag will vote on establishing a European financial stability mechanism, which will take the place of the present temporary bailout fund. This third vote is not expected before December. A rejection of any of these measures from the eurozone's key economy would give financial markets a seismic shock.

Hurdle 2: The Troika decision on releasing bailout funds

The delegation made up of officials from the European Central Bank, European Commission and International Monetary Fund, will decide next month whether to release €8bn in bailout funds to Athens. If that money is not delivered, Greece will run out of money to pay debtors and default on its loans. That would send financial markets into meltdown. Release of the funds depends on the Greek government meeting commitments to make massive cuts to state spending and push through large tax rises. The Greek Prime Minister, George Papandreou, promised German leaders this week that Greece will "meet all its commitments".

Hurdle 3: Greece votes on austerity budget

On Tuesday, the Greek parliament approved a key new revenue-raising property tax. However, the country's Finance Minister, Evangelos Venizelos, said this week that pivotal elements of the latest government budget plans will not be presented to lawmakers for approval until the end of October. Meanwhile, pressure is growing on Greek politicians from the street. Protesters continue to gather in Athens' Syntagma Square and more public sector strikes are promised by unions. The Socialist government, whose majority consists of just a handful of deputies in the 300-seat Greek assembly, is extremely fragile.

Hurdle 4: Slovakian parliament votes on bailout