Germany is poised to approve on Friday the lion's share of a $1 trillion safety net for financially troubled euro zone nations as an EU task force looks to toughen regulations within the bloc blighted by a debt crisis that has cast a pall over global economic health.

Germany's lower house of parliament is due to vote on the 750 billion euro rescue package that is unpopular with voters at around 6 a.m. ET.

Europe's biggest economy may have to fork out up to 148 billion euros in guarantees, on top of an equally divisive 22.4 billion euro contribution to a package for debt-ridden Greece.

Chancellor Angela Merkel's center-right coalition has the necessary clout to get the bill passed, but it wants as much cross-party backing as possible to ease the public opposition to bailing out weaker euro zone states.

Still, Merkel may have to pay a price. The opposition Social Democrats are threatening to abstain from Friday's vote unless the government backs a motion to push for an international financial transaction tax.

The vote follows pledges by Germany and France on Thursday to set aside differences and work together to solve the European debt crisis and support the euro, which plunged to a four-year low this week, rattling confidence across the globe.

On Thursday, the United States also took a big step closer to the most comprehensive overhaul of Wall Street rules since the 1930s after a financial reform bill cleared a final Senate vote.

These tougher rules are aimed at preventing a recurrence of the 2007-2009 crisis which plunged the global economy into a recession that it is still struggling to shake off today.

The bill has to be merged with one from the U.S. House of Representatives, but analysts said they expected President Barack Obama to sign the law as soon as next month.

France and Germany, co-founders of the euro, had clashed over a unilateral German ban on some speculative trades on Wednesday, but their public patching up helped, along with short-covering, push the euro on Friday up to $1.26 from its four-year low of $1.2143 on Wednesday.

Tokyo's benchmark Nikkei average fell more than 2 percent, extending heavy losses seen on Wall Street. Shares elsewhere in Asia dropped around half a percent.

A German spokesman said Merkel and French President Nicolas Sarkozy had agreed to cooperate on euro-zone growth strategies and coordinate their positions on world financial rules at a G20 summit next month. Sarkozy will also visit Berlin on June 7.

MAMMOTH TASK

The Franco-German dispute highlights the mammoth mission ahead for EU finance ministers meeting on Friday to discuss reinforcing economic surveillance and budget discipline to avoid another Greek-style debt crisis in the euro area.

The talks are however being undermined even before they begin, with some countries opposing a call by the European Commission to see member's budget plans before they are submitted to their own parliaments.

This demand is one of several by the Commission, but countries feel it threatens their sovereignty.

That in turn has raised concerns the EU, which represents more than 500 million people, will miss the best chance in years to agree on far-reaching reforms to stabilize the euro.

The EU will have to cobble something together by the end of this year but it is an open question whether it will be meaningful or not, said Daniel Gros, director of the Centre for European Policy Studies think tank.

If you're in a situation where you have months to agree and everyone wants it be as perfect as possible on paper, but in reality containing as few constraints as possible on member states, the situation is completely different.

U.S. Treasury Secretary Timothy Geithner will visit Europe next week, on his way back from a trip to China, and will meet the head of the European Central Bank (ECB) and other officials.

RESTORING CONFIDENCE

China said the crisis was adding to uncertainty, with Zhu Guangyao, assistant finance minister, calling it a challenge to the stability of the entire international financial market.

The euro for now is a secondary story. The danger is that people are doubting the sustainability of the global recovery, said Boris Schlossberg, director of research at GFT Forex in New York. It's bigger than the euro because everything is so intrinsically woven together.

The euro has lost more than 12 percent against the dollar this year, shedding 7 percent over the last month.

The ECB has also taken the unprecedented step of buying euro-denominated government debt to help stabilize markets.

Germany has said restoring confidence in the euro was its top priority, demanding tougher regulation and oversight.

But France, smarting from Germany's failure to consult on the trading ban, disagrees, but Sarkozy said France would enshrine in its constitution a commitment to cut its budget deficit.

Though far less constraining than Germany's debt brake, which would force the federal government to limit the deficit to 0.35 percent of national output by 2016, France's move highlights how the debt crisis is forcing all euro zone countries to cut back on spending and trim their deficits.

Early this month, Greece was forced to adopt steep spending cuts and tax hikes in exchange for a 110 billion euro ($135 billion) bailout from other euro zone governments and the International Monetary Fund.

Last week Spain and Portugal, struggling with high deficits that prompted investors to drive up their borrowing costs, announced new deficit-cutting measures. Italy is planning deficit reduction steps, as well, while France has proclaimed a three-year public spending freeze.

(Writing by Miral Fahmy in Singapore; Editing by Neil Fullick)