Some of the high-profile defendants include pharmaceutical giants Johnson & Johnson, Purdue Pharma and Teva Pharmaceuticals, large distributors McKesson and Cardinal Health and pharmacy chains like CVS, Rite Aid and Walgreens.

Mr. Sessions called the opioid addiction crisis “beyond imagining” during separate remarks on Tuesday morning at the National Association of Attorneys General. He said the government would take a hard look at doctors who overprescribe prescription painkillers, which can lead to addiction and abuse of illegal drugs like heroin.

Mr. Sessions has described the opioid epidemic as a national health crisis and estimates that 64,000 Americans died of drug overdoses in 2016, a record increase. The vast majority of those deaths, he said, happened after users took opioids like prescription painkillers, heroin and fentanyl.

He also called the opioid crisis a significant drain on federal resources, costing the government $115 billion in 2017 and $1 trillion since 2001. He predicted that it could cost the United States an additional $500 billion over the next three years.

The attorney general is legally able to argue on behalf of the government’s interest in any court in the country via a statement of interest, which does not make the government a plaintiff. Mr. Sessions’s announcement on Tuesday followed a significant dispute in the case in Ohio.

On Monday, lawyers for the Drug Enforcement Administration attended a hearing in the Ohio courtroom about how much data they would share about the national distribution of painkillers.

Insisting that it did not want to compromise ongoing criminal investigations, the agency offered to provide two years’ worth of information in the case. Judge Dan Aaron Polster has given the agency until next Monday to decide whether it will comply with his request to provide the sides with nine years of data. Determining the number of pills, the location and the distributors can be a major factor in assigning liability.

Richard Fields, a lawyer who represents state attorneys general and sovereign Native American nations in opioid litigation, predicted that the statement of interest “will help unlock this data so that we can hold manufacturers, distributors and pharmacies accountable for flooding communities with pills.”