Amazon is open to supporting third-party voice assistants like Apple's Siri or Google Assistant on its Echo speakers, the company's senior VP of devices said on Wednesday.

"If Apple or Google want to come call, my phone number is out there. They can call," David Limp remarked to CNBC. "I hope there is a day when that happens. I don't know if I can envision it, but I hope it happens, on behalf of customers."

Currently the Echo line uses Amazon's Alexa assistant, which has been popular enough to spread to other devices, including third-party offerings like phones and thermostats. It in fact spawned the entire "smartspeaker" product category — Amazon's main competition being the Google Home, and Apple's newly-announced HomePod, coming in December. Microsoft is meanwhile working with partners on Cortana-enabled speakers.

While Google has been eager to put Assistant on third-party hardware, Apple has so far reserved Siri exclusively for its own products. It's therefore unlikely that Siri will appear on an Echo anytime soon.

The HomePod takes a different tack than most smartspeakers, concentrating on high-end audio with features like seven tweeters, a subwoofer, and beamforming for vocals. It will also sell for a much higher pricetag — $349, about $169 more than the standard Echo, and $220 more than the Google Home. An Echo Dot is just $49.99, though it requires existing speakers for quality sound.