A global tax to help fight AIDS, as proposed by French President Jacques Chirac, would not be fully effective unless every country in the world was involved, Japan’s top financial diplomat said on Thursday.

Chirac told the World Economic Forum on Wednesday that such a tax, which he said could be imposed on financial transactions or airline tickets, could raise up to $10 billion annually.

But Japan’s vice finance minister for international affairs, Hiroshi Watanabe, said that unless all countries were involved, business would simply move to where the tax was not imposed.

“The problem with an international tax is that unless all countries impose such a tax, there will be a hole in the framework,” Watanabe told reporters. “I think that imposing international taxes on financial transactions or airline tickets would be difficult to do.”

Watanabe said Japanese authorities would keep an open mind about such proposals, but he thought it would better for governments to allocate more of their development assistance budgets to help finance the fight against AIDS.