An experimental 'space junk' collector designed to pull rubbish from the Earth's orbit has run into trouble, Japanese scientists said Tuesday, potentially a new embarrassment for Tokyo's high-tech programme.

Over 100 million pieces of garbage are thought to be whizzing around the planet, including cast-off equipment from old satellites and bits of rocket, which experts say pose a growing threat to future space exploration.

Scientists at the Japan Aerospace Exploration Agency (JAXA) are testing an electrodynamic 'tether' -- created with the help of a fishing net company -- to slow the junk down and bring it into a lower orbit.

The hope was that the clutter -- built up after more than five decades of human space exploration -- would enter the Earth's atmosphere and burn up harmlessly long before it has a chance to crash to the planet.

About 700 metres (2,300 feet) in length, the tether was due to be extended out from a cargo ship launched in December carrying supplies for astronauts at the International Space Station.

But JAXA says it is not sure if the tether, made from thin wires of stainless steel and aluminium, successfully deployed or not.

JAXA will continue trying to remedy the situation before the cargo ship is expected to reenter the atmosphere on Saturday, the agency added.

The trouble comes just two weeks after JAXA had to abort a mission intended to use a mini-rocket to send a satellite into orbit after the spacecraft stopped sending data to ground control shortly after liftoff.

A pricey ultra-high-tech satellite launched in February last year to search for X-rays emanating from black holes and galaxy clusters but was ultimately abandoned after researchers said contact with it had been lost.