The Group of 20 leading economies could step up the battle against tax evasion using offshore accounts in its meetings Thursday and Friday, officials said.
The G20 is expected to weigh endorsing a global effort to force banks to automatically share information with countries seeking to tax their nationals holding secret offshore accounts -- an effort that could deal a blow to tax havens like the Cayman Islands, Hong Kong, Switzerland and others.
It remained unclear how far the G20 will go. At least the United States and France are said to be hoping for a strong endorsement.
But even continued discussion will confirm how far a once-disdained effort by the United States alone to collect taxes on US nationals' offshore accounts has expanded and gained support among other major economies, especially those facing large holes in their budgets.
"The issue is to go as far as possible," said one European official, speaking on condition of anonymity.
"Will they set a new standard, or simply recognize it in principle? We will see."
Supporters want banks to automatically supply information to a country on the accounts of its nationals, in the way the US FATCA -- the Foreign Account Tax Compliance Act -- requires information on Americans' accounts abroad.
"A door toward the end of banking secrecy is open. It is something extremely important," said French Finance Minister Pierre Moscovici ahead of the G20 meeting late Thursday.
There is "an unstoppable movement toward a 'European FATCA'" he said, but that and the US effort need to be elevated to the level of the G20.
Pushing the issue on the institutional level is the Organisation for Economic Co-operation and Development (OECD), whose Global Forum on Transparency and Exchange of Information for Tax Purposes is helping set standards and advance commitment to the effort.
The European crisis has heightened the issue of tax evasion in the eurozone, and more countries have shown interest.
A scandal over an offshore account of France's budget minister Jerome Cahuzac led to his resignation and being charged with tax fraud.
On Monday, all 38 ministers in President Francois Hollande's cabinet were ordered to publicly disclose their personal wealth -- a first in France -- and the government will attempt to have the disclosure rule extended to parliamentarians in a bill to be introduced on April 24.
On April 11 offshore banking haven Luxembourg gave up its opposition to the effort, saying it would begin automatic sharing of account information related to people residing in the European Union.
On Thursday Transparency International called for G20 finance chiefs to endorse a global system for the automatic exchange of bank data.
"The G20 finance ministers have the power to stop corrupt people hiding behind secret bank accounts and opaque corporate structures," the head of the anti-corruption watchdog, Huguette Labelle, said in a statement.