Public officials have long urged makers of powerful painkillers to do more to make the medications harder to crush and abuse. But now that some companies have done so, they want something in return — a ban on generic versions of the drugs they make that do not have such tamper-resistant designs.

In coming months, generic drug producers are expected to introduce cheaper versions of OxyContin and Opana, two long-acting narcotic painkillers, or opioids, that are widely abused.

But in hopes of delaying the move to generics, the makers of the brand name drugs, Purdue Pharma and Endo Pharmaceuticals, have introduced versions that are more resistant to crushing or melting, techniques abusers use to release the pills’ narcotic payloads.

The two drug makers, which say they are motivated not by profit but by public safety, have also been waging a multifront political and legal war to block sales of generics that are not tamper-resistant.