The world's top body for economic coordination unveiled itsblueprint Monday for cracking down on international tax avoidance,an opening salvo in what promises to be a prolonged battle betweencountries and companies over who gets taxed and where.

The Organization for Economic Cooperation and Development, aresearch institute funded by 34 countries including the U.S., isseeking to curb tax haven use and other strategies by companiessuch as Google, Starbucks and Apple, which the group says costs theworld as much as $240 billion a year in lost revenue.

“This is the most important development in international tax inquite a few decades,” said H. David Rosenbloom, an attorney atCaplin & Drysdale in Washington and director of theinternational tax program at New York University's School of Law.“It will definitely make a difference. Exactly what that differencewill be is hard to predict.”