Amazon insisted Wednesday on a significant change to proposed US drone regulations before it introduces 30-minute Prime Air parcel delivery by unmanned aerial vehicles to its American customers.

The online retail giant -- a major player in the development of UAVs for civilian missions -- acknowledged safety concerns as the Federal Aviation Administration hammers out a final set of commercial drone-flying rules.

But it balked at the FAA's proposal, set out in a notice of proposed rulemaking in February, that small UAVs fly only in full view of their operators on the ground -- not at a distance beyond the line of sight.

"If adopted as drafted, the rules would not establish a regulatory framework to permit Prime Air operations in the United States," Amazon's vice president for global public policy Paul Misener told lawmakers.

Amazon disagrees with the FAA's claim that flying drones beyond their operators' line of sight is a major safety concern, Misener told the House of Representatives Committee on Oversight and Government Reform.

"Although these safety concerns present particular engineering challenges, to be sure, such challenges are not qualitatively different from other engineering challenges facing small UAS (unmanned aerial systems) designers, so they should be assessed starting now, ultimately resulting in performance-based operating permissions," he said.

The FAA is poised to miss a September deadline for a long-awaited final set of rules to govern civilian drones in crowded US skies -- prompting industry fears that the United States is falling behind other countries in developing high-value UAV technology.

FAA Deputy Administrator Michael Whitaker told the panel that rules governing drones weighing less than 55 pounds (25 kilograms) should now be in place within a year from now.

Until then, he said, the agency is sifting through about 4,500 comments it received since issuing its notice four months ago.

The FAA has also been issuing exemptions and waivers to the current near-ban on commercial drone usage at a rate of about 50 per week, Whitaker said.

As the world's largest online retailer, Amazon raised eyebrows in late 2013 with its plan to airlift small parcels to customers by drone in select markets, less than 30 minutes after an order is received.

Frustrated by the lack of clear US rules, it has gone to other countries to flight-test its evolving technology, including a secret location in the western Canadian province of British Columbia.

Flying typically about 200 feet (60 meters) above ground, Prime Air drones "will take advantage of sophisticated 'sense and avoid' technology as well as a high degree of automation to safely operate at distances of 10 miles (16 kilometers) or more, well beyond visual line of sight," Misener testified.

Brian Wynne, president of the Association for Unmanned Vehicle Systems International industry group, said UAVs are "poised to be one of the fastest-growing industries in American history," bringing more than $82 billion and more than 100,000 jobs to the nation's economy.

But advocacy director Harley Geiger of the non-profit Center for Democracy and Technology echoed privacy concerns, citing "nightmare scenarios," such as relentless police tracking of individuals, or corporations using drones to monitor people's behavior even on private property.

"Few existing laws would stand in the way, and the public does not trust the discretion of government or the UAS industry to prevent these scenarios from approaching reality," he said.

Sixteen states have enacted their own UAV privacy laws since 2014, but the US Supreme Court has repeatedly ruled since the 1980s that Americans have no "reasonable expectation of privacy" from airborne government surveillance, he said.