Washington ? President Bush plans to propose new rules designed to make it easier for Americans to buy generic medicine by reining in the ability of brand-name pharmaceutical companies to keep lower-price drugs off the market.

Administration officials Sunday night estimated the plan, which could take effect within the next several months, could shave $3 billion a year off the nation’s rapidly escalating expenditures on prescription drugs.

The White House is responding to criticism of the health industry, including in a recent federal study, that has accused the companies of exploiting loopholes in the law to thwart competition and thus increase the price of many medications for patients, employers and government-run insurance programs.