Fissures are suddenly forming along the edges of the giant iceberg of America’s multibillion-dollar “war” on drug use, first formally proclaimed by President Richard Nixon in 1971.

But so much depends on what President Barack Obama decides to do with the issue.

This month a Latin American commission headed by former Presidents Fernando Henrique Cardoso of Brazil, Ernesto Zedillo of Mexico and Cesar Gaviria of Colombia condemned harsh U.S. drug prohibition policies that are based, in Gaviria’s words, “on prejudices and fears and not on results.”

Fueled by Americans’ drug appetite and dollars, drug-gang violence is engulfing Mexico, threatening the very stability of the state with massive corruption and close to 6,000 killings last year.

Brazil is afflicted with daily gun battles between police and gangs in urban slums. And despite years of intensive U.S.-backed efforts to eradicate Colombia’s cocaine exports, official reports show they’ve risen 15 percent in this decade. A high proportion are smuggled into the U.S.

The drug war, the former presidents charge, is imperiling Latin America’s democratic institutions and corrupting “judicial systems, governments, the political system and especially the police forces.”

As both the world’s largest drug consumer market and the lead voice in setting global drug policy, the United States, the Latin leaders argue, has huge responsibility now to “break the taboo” that’s suffocated open debate about the wisdom of a clearly failed 38-year “war.”

The leaders are placing hopes in Obama, who as a candidate said the “war on drugs is an utter failure” and talked favorably about more public health-based approaches.

Given that history, and given this president’s openness to hearing diverse points of view, it’s hard to believe he’ll maintain the stony wall of indifference to drug policy reform that all his predecessors since Nixon have maintained.

Still, there are crucial issues of politics and timing. One can just imagine White House advisers telling Obama to steer clear of the drug issue, that it could be as perilous and distracting as gays in the military were for President Bill Clinton in his first year in office.

Against that background, the Latin leaders’ statement itself may help move the compass. Ethan Nadelmann, executive director of the Drug Policy Alliance, calls their manifesto (www.drugsanddemocracy.org) “a major leap forward in the global drug policy debate.” One reason: these are conservative, highly respected leaders.

Gaviria, as president of Colombia in the early ’90s, for example, worked with U.S. anti-narcotics agents to hunt down and kill Pablo Escobar, the cocaine kingpin.

But Gaviria and his fellow former presidents, along with Latin mayors, writers and other respected leaders joining in their declaration, say it’s time to recognize that force and prohibition have failed to stop dangerous narco-trafficking.

It’s high time, they propose, to focus on harm reduction and prevention efforts — following European models to change the status of addicts from drug buyers in an illegal system to that of patients cared for in a public health system. They also suggest considering decriminalizing possession of marijuana for personal use — a step Obama recently indicated he’s not ready to take.

And they say they’ll be watching how the U.S. handles the meeting of a key United Nations-sponsored Commission on Narcotic Drugs which convenes in Vienna next month. The commission is to review the prevailing, harsh, U.S.-molded drug policies the U.N. General Assembly set in 1998. But there’s the question: Will Obama (and Hillary Clinton’s State Department) send reformers, or just bureaucrats who’ve soldiered in our blind-alley war on drugs? Drug reformers were disappointed when Obama recently passed over public health advocates to appoint a police chief — Gil Kerlikowske of Seattle — as the country’s new drug czar (director of the Office of National Drug Control Policy).

But Kerlikowske does appear to have worked harmoniously with Seattle’s cutting edge of drug reforms — well-established needle exchange programs, marijuana arrests declared the lowest law enforcement priority through public initiative, and a local bar association that’s a national model in finding alternatives to drug prohibition laws.

So there are gleams of hope at the end of a long tunnel. And what better time than this wrenching recession to shift law enforcement to legitimately serious crimes, starting to discharge the hundreds of nonviolent drug offenders held in our bulging, cost-heavy jails and prisons?

Predictably, any shift will be tough. Many law enforcement agencies count on the jobs — and seizures of cash — that the drug “war” delivers. Our “prison-industrial complex,” guard unions included, remains potent. And federal law actually prohibits the drug czar from recommending legalization of any proscribed drug, no matter what his personal judgment may be.

We have dug ourselves a deep hole. Only forthright and courageous leadership is likely to start us on a saner path. Can this be “the time?” Please, Mr. President.

Neal Peirce’s e-mail address is nrp@citistates.com.