BOGOTA, Colombia (AP) – American-backed counter-narcotic programs in Colombia and Mexico are disrupting the flow of cocaine into the United States, driving up prices 44 percent on U.S. streets this year, the White House drug czar said Thursday.

John Walters told reporters that the average price per pure gram of cocaine rose 44 percent to $136.93 between January and September. He said the jump, detected in 37 cities, was accompanied by a 15 percent decline in the average purity of cocaine, another key indicator of supply.

“We’ve never had disruptions of this magnitude before,” Walters said in Bogota, where he’s on a two-day visit with Drug Enforcement Agency chief Karen Tandy to show support for Colombia’s anti-narcotics strategy.

Drug policy analysts disputed Walters’ upbeat appraisal as possibly unfounded. A Justice Department drug intelligence report released Wednesday indicates prices since July may already be returning to earlier levels in some markets.

“The increase (Walters) is claiming is decent-sized, but it’s not unprecedented and history shows that those price spikes reverse quite quickly,” said John Walsh, a drug policy expert at the Washington Office on Latin America, which has criticized the anti-drugs strategy.

Despite a record eradication campaign that’s been at the heart of $5 billion in American foreign aid to Colombia since 2000, production of coca – the base ingredient of cocaine – continues to rise, the latest White House survey found.

Colombia supplies 90 percent of America’s cocaine.

But Walters said he believes the price increases can be sustained.

“Nine months isn’t temporary in my view,” he said. “At some point to say this just a blip gets a little harder to argue.”

Key lawmakers have slammed Walters in the past for touting the drug war’s achievements.

Last year Sen. Charles Grassley, a Republican from Iowa who then chaired the Senate Caucus on International Narcotics Control, called for President Bush to fire Walters for “cooking the books” and celebrating in November 2005 a 19 percent, six-month price hike that was later reversed.

This year’s apparent shortage could prove to be just as short-lived, the 2008 National Drug Threat Assessment found.

Even while acknowledging previously announced shortages during the first half of the year, the report prepared by the Justice Department’s drug intelligence center found “cocaine availability may already be returning to previous levels in some areas.”

The report did not say which markets were being replenished or how quickly, only that the shortage observed between January and June “was not the result of decrease in cocaine production.”

More likely, it was the result of a crackdown on prominent Mexican traffickers, violent feuding among that country’s cartels and surging demand for cocaine in Europe.

“Because cocaine production in South America appears to be stable or increasing, cocaine availability could return to normal levels during late 2007 and early 2008,” the report states.

The Justice Department report echoes the findings of another study presented to Congress on Oct. 25 by the Government Accountability Office.

“Nobody believes there’s not enough drugs in the system to satisfy global demand,” Jess Ford, author of the GAO study partly based on the most recent government data, told The Associated Press.