WASHINGTON, June 15 (Reuters) - U.S. lawmakers from both parties pressed Alphabet Inc’s (GOOGL.O) Google and Amazon.com (AMZN.O) on Tuesday about their smart speakers markets, amid concern over the domination of the tech behemoths in this area. Senator Amy Klobuchar, chair of the Senate Judiciary Committee"s antitrust subcommittee, noted that Amazon had more than 50% of the smart speaker market while Google had 30%, and stressed the importance of interoperability. "In a few years, people might easily have 20 or more connected devices in their homes – from a vacuum and a fridge to speakers and lights. We want those devices to work with each other seamlessly," she said. "You shouldn"t have to choose the right devices for your home based on whether they play nicely with Google or Amazon"s digital assistants." Smart home technology includes smart speakers like Amazon"s Echo or Google"s Nest, security systems or televisions. Google Senior Public Policy Director Wilson White said interoperability was a goal and there were "robust conversations" underway on how to achieve it. Ryan McCrate, Amazon"s associate general counsel, said Amazon wanted users to have access to multiple assistants from a single device if that was what the user wanted. Neither Google nor Amazon appeared to be trying for true interoperability, said Eddie Lazarus, chief legal officer for smart speaker maker Sonos. Google contractually prohibits Sonos from using technology that allows users to switch between Amazon"s Alexa and the Google voice assistant, Lazarus said. He said Amazon"s effort to work with smaller companies was "just an on-ramp into the Amazon ecosystem because you can"t mix and match between the big companies." The hearing took place at a time of extraordinary interest in tougher antitrust enforcement, much of it focused on the biggest U.S. technology companies. One result has been a series of investigations and several federal and state lawsuits filed against Google and Facebook as well as a long list of antitrust bills.