President Clinton yesterday signed into law legislation that would maintain stiff prison sentences for those convicted of possessing or trafficking in small amounts of crack cocaine, over the objections of some civil rights groups and the Congressional Black Caucus.

In taking the action, Clinton aligned himself with congressional Republicans, who rejected recommendations by the U.S. Sentencing Commission to lower the prison terms for offenses involving crack cocaine to make them the same as offenses involving powder cocaine.

In a written statement emphasizing his anti-crime record, Clinton said he was rejecting "dramatic reductions" in penalties for possessing and selling crack cocaine because trafficking in that drug "has had a devastating impact" on communities across the nation, particularly inner-city communities. "I am not going to let anyone who peddles drugs get the idea that the cost of doing business is going down," Clinton said.

The current penalties, which Clinton's action endorsed, have been criticized for the disparity between the punishment for those convicted of possessing or selling crack cocaine, who generally are black, and those dealing in powder cocaine, who generally are white. Crack cocaine is a form of cocaine cooked with baking soda that is cheaper and more accessible than powder cocaine.

Possession of five grams of crack brings a mandatory five-year prison term, while possession of the same amount of powder cocaine draws a one-year sentence.

Trafficking in five grams of crack brings the same five-year prison term as trafficking in 500 grams of powder cocaine, creating what critics called a 100-to-1 ratio.

Clinton acknowledged those disparities, saying that "some adjustment is warranted," and he endorsed the sentencing commission's reviewing the issue further. He also said the way to fix the disparity is to increase the penalty for distributing powder cocaine. Clinton said he had ordered Attorney General Janet Reno to "develop enforcement strategies" to go after powder cocaine distributors.

Clinton's move was an endorsement of legislation passed by the Republican-controlled House and Senate that killed the recommendations of the U.S. Sentencing Commission -- the first time in the commission's seven-year history that Congress and the White House had blocked one of its recommendations. The commission had recommended moderating the penalties for crack cocaine possession to bring those penalties in line with powder cocaine possession.

Critics accused Clinton of making a purely political call, fearful of looking soft on crime. Jesse L. Jackson, who last week met with White House Deputy Chief of Staff Harold Ickes to lobby in favor of changing the penalties, said yesterday that Clinton's decision was "a moral disgrace."

Jackson said Clinton "is willing to sacrifice young black youth for white fear" and added, "There are those inside the White House who are willing to write off the black Democratic vote to look tough to white Republican voters." He said Clinton and Reno both know that "crack is code for black" and that in rejecting a change, the Clinton administration is consciously and with political intent playing to white conservative voters with a Republican anti-crime agenda.

The White House did emphasize, in its announcement yesterday, the anti-crime elements of the decision. Along with the presidential statement, it released statements by the Fraternal Order of Police, the National Association of Police Organizations and the National Sheriff's Association calling for a rejection of the sentencing commission recommendations.

The Congressional Black Caucus last week sent Clinton a letter arguing that the disparities "make a mockery of justice" because they "fuel the appearance of unfairness" by undermining faith in equal protection under the law.

The disparities provoked an impassioned debate in Congress, with some arguing that crack cocaine is more psychologically addicting and more associated with violent crimes. But others argued that the disparities for the same drug were a function of wealthy whites protecting their children.

"If somebody is convicted of selling $225 worth of crack cocaine, they get the same penalty as somebody who sells $50,000 worth of powder cocaine," Rep. Melvin Watt (D-N.C.) said. "Poor young kids who can afford only crack go to jail. Rich young kids who can afford powder go home and sleep in their own beds."

Recent riots at several federal prisons were attributed, at least in part, to anger over the sentencing disparities after the House last month refused to accept the recommendations to equalize the base penalty for crack and cocaine crimes.

Since the riots and anticipating disturbances in the wake of Clinton's decision, the Justice Department has taken steps to "upgrade the level of security" at federal prisons.

Of the 85 federal prisons, "65 are operating under normal procedures," Justice Department spokesman Carl Stern said. "Nine remain in a lock-down," he said, including those where disturbances broke out, and 11 others have some increased security measures in effect.

But prison officials have taken "additional security steps," a department official said, in anticipation of Clinton's signing the bill, including making sure that "an adequate or greater number of guards are available" in the event of trouble. "It's only normal whenever we think there might be a precipitating factor for unrest in the institutions."