The draft is being finalized by the chairman of the Senate Intelligence Committee, Sen. Richard Burr, R-N.C., and the top Democrat, Sen. Dianne Feinstein of California.
Their goal, they said in a statement, is to ensure adherence to any court order that requires helping law enforcement or providing decrypted information. "No individual or company is above the law."
It was not immediately clear when they would introduce the bill.
The draft language ran into opposition from another committee member, Sen. Ron Wyden, D-Ore., who said the proposal would require "American companies to build a backdoor" into devices.
"They would be required by federal law per this statute to decide how to weaken their products to make Americans less safe," he said. Wyden pledged to do "everything in my power" to prevent the plan from passing.
The emerging measure follows the Justice Department's battle with Apple Inc. over access to an encrypted and locked iPhone - a fight pitting digital privacy rights against national security concerns.
The Justice Department dropped its legal effort to compel Apple to provide it with specialized software that would allow the FBI to hack into an iPhone that was issued to San Bernardino County, California, health inspector Syed Farook. Farook and his wife, Tashfeen Malik, killed 14 people in December. The couple died in a shootout with authorities.
The iPhone was found in a vehicle the day after the shooting. Two personal phones were found destroyed so completely the FBI could not recover information from them.
U.S. Magistrate Sheri Pym had ordered Apple to provide the FBI with software to help it hack into Farook's work-issued iPhone after the government said only Apple could help authorities access the encrypted and locked iPhone. But days before a hearing in the case an outside party showed the FBI an ultimately workable situation to hack the phone.