A national medical group Thursday abruptly canceled its plans to train doctors about marijuana for pain relief after a federal agency pulled its funding.

The episode highlights an ongoing conflict between federal and state laws on marijuana.

The American Academy of Pain Medicine scrubbed its plans for a one-hour online course next month after a request from the U.S. government agency that provided the funding, a spokeswoman for the pain medicine group said. The money came from the Substance Abuse and Mental Health Services Administration, or SAMHSA.

"We cannot speak to the reason that SAMHSA has asked that we not proceed with this webinar, but the webinar will no longer take place," spokeswoman Megan Drumm in an email Thursday

The group had informed a coalition of medical groups overseeing the government money about the course title and its learning objectives, Drumm said.

But after an inquiry from The Associated Press this week, the federal agency said the coalition that gave the grant would no longer take part.

While marijuana is considered an illegal drug by federal officials, 29 states have authorized its use for medical purposes. Nine of those states require doctors to get training before they can recommend medical marijuana. Some states have hired private companies to design educational programs. The seminar would have been the first offered by the pain group.

Part of the U.S. Department of Health and Human Services, SAMHSA oversees more than $1 billion in grants to fight opioid addiction and is headed by Dr. Elinore McCance-Katz, who has been outspoken about the dangers of marijuana. She has opposed the idea that marijuana could help chronic pain patients use fewer opioid medicines.

Agency spokesman Chris Garrett said in an email that the coalition would not be participating but he did not respond to questions asking why the Providers Clinical Support System would not take part or if the agency had asked the pain medicine group to cancel the training.

Doctors should be able to learn about medical marijuana from trusted sources that are free from commercial bias, said Dr. Graham McMahon, president and CEO of Accreditation Council for Continuing Medical Education.

"It's important that the public get accurate information from their doctors and that doctors get accurate information from educators," he said.

McMahon's nonprofit group accredits organizations that offer continuing medical education, which doctors need to maintain their licenses and hospital credentials. The group recently published guidance for training on cannabis.

There's evidence marijuana can treat chronic pain in adults, according to a report last year from the National Academies of Sciences, Engineering and Medicine. That report also concluded the lack of scientific information about marijuana poses a risk to public health.

Scheduled speakers for the July 26 course were pain doctors from the University of Texas and the University of California, San Diego. They planned to cover how to select patients for medical cannabis, appropriate products and doses and how to "wean opioids in patients on chronic opioid therapy," according to the course description.CARLA K. JOHNSON, AP

[cover photo Ted S. Warren, AP]