LONDON (AP) -- Taxing financial trades has been touted as a panacea for all kinds of global ills, a cash source to fight poverty and global warming. But the latest European attempt to introduce a worldwide standard 40 years after it was first conceived is facing stiff opposition from the U.S. and Britain.Jose Manuel Barroso, the president of the EU's executive arm, on Wednesday threw his weight behind the tax that his office estimated could raise euro57 billion ($77 billion) a year in Europe to help combat a debt crisis that is threatening the euro currency."In the last three years, member states have granted aid and provided guarantees of euro4.6 trillion to the financial sector," Barroso said. "It is time for the financial sector to make a contribution back to society."The tax would be a tiny percentage of the value of a trade in assets like stocks and bonds. Although some countries already have a minimal duty on share trading, the new proposal would not only increase the scope and size of the tax but also siphon off some revenue to Brussels.The European Commission has formally backed the tax to take effect from January 2014.As a result of the financial crisis in 2008 and the ensuing recession, debt levels across Europe, and not just in the bailed out countries of Greece, Ireland and Portugal, have risen sharply. Across the 27-nation EU, debt as a percentage of national income has spiked from below 60 percent in 2007 to 80 percent this year.Though the tax could dent growth and employment, it has won a fair degree of support across the 17-country eurozone, including France and Germany, the EU's two biggest economies.Britain, however, has been adamantly against it unless it is used on a global basis. Its opinion carries weight in the debate because London is the continent's biggest financial center.The argument made by the likes of George Osborne, Britain's finance chief, and echoed last week by his counterpart in the U.S. Timothy Geithner is that the tax just won't work if it's not introduced globally. If it's not, investors can move money quickly to where the tax doesn't need to be paid, saving themselves potentially large sums of money in financial trades.Howard Wheeldon, a senior strategist at BGC Partners, said it's a bad idea to have a trades tax now, especially since many banks are still trying to meet new requirements to beef up capital buffers."The timing is inappropriate; it's something to look at in a few years time," Wheeldon said.Even if Britain and the U.S. decide to opt out, it is possible that the eurozone countries, or at least some of them, may go it alone."I think the eurozone or number of member states would go ahead and do it, and would start it at a low enough level to answer political objections," said Sony Kapoor, managing director of Re-Define, an economic think tank.Some activists campaigning for the tax worry the money may be used solely to fix the world's financial difficulties. They say a large chunk of the revenues should be used for other important issues, such as reducing poverty or fighting global warming.Oxfam International, a long-time proponent of the tax, lauded the European Commission's support ahead of the October 17-18 summit of EU leaders and the Group of 20 meeting of the leaders from the top industrial and developing nations."The financial transaction tax is moving from rhetoric to reality but a significant part of the revenues should be used as Bill Gates suggested, to help poor countries facing chilling reductions in aid, trade, and investment -- not just shore up the EU budget," said Nicolas Mombrial, Oxfam International's EU policy advisor. The multibillionaire Microsoft founder has been commissioned by the G-20 to produce a report on development financing and is considering the potential of the tax.Oxfam's Mombrial also argues that the rate of the tax should be higher than the 0.1 percent levy on shares and bonds proposed by the EU."It's clear that higher rates are perfectly feasible and would raise more money to tackle poverty," Mombrial said, noting that a 0.5 percent tax already applies to share trades in the U.K.The motivations behind the tax are a long way from the designs of Nobel Prize laureate James Tobin, who first made his proposal for the flat tax on currency transactions in the early 1970s when U.S. President Richard Nixon ended the dollar's convertibility to gold and effectively brought an end to the global currency system that had prevailed since World War II.Tobin said at the time that the tax would help limit instability arising from a world of floating exchange rates."Financial transaction taxes, appropriately designed, can not only raise substantial revenue but also enhance stability by discouraging destabilizing trading that serves little economic purpose," Re-Define's Kapoor said.