Scientists at a conference in the United States are asking for public consent to actively try to contact intelligent life on other worlds.
The appeal was made at the American Association for the Advancement of Science (AAAS) meeting in San Jose because of concerns about potential risks if intelligent life is alerted to Earth.
Researchers at the Search for Extra Terrestrial Intelligence (Seti) Institute have been listening for signals from outer space for more than 30 years using radio telescope facilities in the US.
The organisation's director, Dr Seth Shostak, told attendees to the AAAS meeting that it was now time to step up the search.
"Some of us at the institute are interested in 'active Seti', not just listening but broadcasting something to some nearby stars because maybe there is some chance that if you wake somebody up you'll get a response," he told BBC News.
"A lot of people are against active Seti because it is dangerous. It is like shouting in the jungle. You don't know what is out there; you better not do it. If you incite the aliens to obliterate the planet, you wouldn't want that on your tombstone, right?"
He said he did not see any incentive for aliens - if they exist - to do that.
"Beyond that, we have been telling them willy-nilly that we are here for 70 years now. They are not very interesting messages but the early TV broadcasts, the early radio, the radar from the Second World War - all that has leaked off the Earth.
"Any society that could come here and ruin our whole day by incinerating the planet already knows we are here.
First contact 'does not go well'
Science fiction writer David Brin, who also spoke at the AAAS meeting, opposed the plan to actively seek intelligent life on other worlds.
"Historians will tell you that first contact between industrial civilisations and indigenous people does not go well," he said.
Mr Brin believed that those in favour of active Seti have been "railroading the public into sending a message without a wide and detailed discussion of what the cultural impact might be".
He did not fear a Hollywood-style alien invasion and thought the likelihood of making contact was extremely low. But the risks, he argued, were extremely high and deserved careful consideration before anyone sent out a signal to potentially habitable worlds.
"The arrogance of shouting into the cosmos without any proper risk assessment defies belief. It is a course that would put our grandchildren at risk."
Leading astronomers, anthropologists and social scientists were expected to gather at Dr Shostak's institute after the AAAS meeting for a symposium to flesh out plans for a proposal for active Seti to put to the public and politicians.