A WAR OF NUMBERS EMERGES OVER COST OF ENLARGING NATO
Rancorous and largely hidden debate over what NATO expansion begins to surface after Sen Jesse Helms, chairman of Foreign Relations Committee, warns that Senate approval of expansion may hinge on what share of cost Europe is willing to pay; evidence suggests that numbers are being adjusted to find balance between Senate conservatives, like Helms, who want to insure that NATO remains credible defensive alliance and European allies who need to cut budget deficits to qualify for single European currency and to pay for expansion of European Union (M)