More than two decades after President Ronald Reagan escalated the war on drugs, arrests for drug sales or, more often, drug possession are still rising. And despite public debate and limited efforts to reduce them, large disparities persist in the rate at which blacks and whites are arrested and imprisoned for drug offenses, even though the two races use illegal drugs at roughly equal rates.

Two new reports, issued Monday by the Sentencing Project in Washington and by Human Rights Watch in New York, both say the racial disparities reflect, in large part, an overwhelming focus of law enforcement on inner-city drug use, with arrests and incarceration the main weapon.

But they note that the murderous crack-related urban violence of the 1980s, which spawned the drug war, has largely subsided, reducing the rationale for a strategy that has sowed mistrust in the justice system among many blacks.

In 2006, according to federal data, drug-related arrests climbed to 1.89 million, up from 1.85 million in 2005 and 581,000 in 1980.

More than four in five of the arrests were for possession of banned substances, rather than for their sale or manufacture. Four in 10 of all drug arrests were for marijuana possession, according to the latest F.B.I. data.

Apart from crowding prisons, one result is a devastating impact on the lives of black men, who are nearly 12 times as likely to be imprisoned for drug convictions than white men, according to the Human Rights Watch report.

Others are arrested for possession of small quantities of drugs and later released, but with a permanent blot on their records anyway.

“The way the war on drugs has been pursued is one of the biggest reasons for the growing racial disparities in criminal justice over all,” said Ryan S. King, a policy analyst with the Sentencing Project, who wrote its report, which focuses on the differential arrest rates, not only between races but also among cities around the country. Some cities pursue urban, minority drug use far more intensively than do others.

Both Democratic presidential candidates, Senator Barack Obama of Illinois and Senator Hillary Rodham Clinton of New York, have strongly condemned the wider racial disparities in arrests and incarceration during their campaigns, although neither has said how to end them.

Two-thirds of those arrested for drug violations in 2006 were white and 33 percent were black, although blacks made up 12.8 percent of the population, F.B.I. data show. National data are not collected on ethnicity, and arrests of Hispanics may be in either category.

“The race question is so entangled in the way the drug war was conceived,” said Jamie Fellner, a senior counsel at Human Rights Watch and the author of the group’s report.

“If the drug issue is still seen as primarily a problem of the black inner city, then we’ll continue to see this enormously disparate impact,” she said.

Her report cites federal data from 2003, the most recent available on this aspect, indicating that blacks constituted 53.5 percent of all who entered prison for a drug conviction.

Some crime experts say that the disparities exist for sound reasons. For example, said Heather MacDonald, a fellow at the Manhattan Institute in New York, blacks and Hispanics are more often involved than whites in the distribution and sale of heroin and cocaine.

Ms. MacDonald said it made sense for the police to focus more on fighting visible drug dealing in the inner city, largely involving minorities, than on hidden use in suburban homes, more often by whites, because the urban street trade is more associated with violence and other crimes and impairs the quality of life.

“The disparities reflect policing decisions to use drug laws to try and reduce violence and to respond to the demand by law-abiding residents in poor neighborhoods to clean up the drug trade,” she said.

But what urban people need is not more incarceration but improved public safety, Mr. King said. “Arresting hundreds of thousands of young African-American men hasn’t ended street-corner drug sales.”

A shift of resources toward drug treatment and social services rather than wholesale incarceration, he asserted, would do more to improve conditions in blighted neighborhoods.

Limited efforts have been made to shift policies in ways that may reduce racial differences. Many states are experimenting with so-called “drug courts,” which send users to treatment rather than prison. This does not, however, affect arrest rates, which have lifelong consequences even for those who are never convicted or imprisoned.

The police in a few cities including Seattle, Oakland, Calif., and Denver have said they are spending fewer resources on arrests for lower-lever offenses like marijuana possession.

In December, the United States Sentencing Commission amended the federal sentencing guidelines for convictions involving crack cocaine, which is more often used by blacks, somewhat reducing the length of sentences compared to those for convictions involving powder cocaine. But mandatory and longer sentences for crack violations remain embedded in federal and state laws.

Copyright 2008 The New York Times Company. Reprinted from The New York Times, National, of Tuesday, May 6, 2008.