Eventually the detritus will enter Earth's atmosphere, burning up harmlessly before it has a chance to crash to the planet's surface.
Since the Soviet-launched Sputnik satellite in 1957, decades of space exploration have produced a hazardous belt of orbiting debris.
Scientists at the Japan Aerospace Exploration Agency (Jaxa) hope to clear up tonnes of space clutter including cast-off equipment from old satellites and pieces of rocket.
Jaxa worked on the project with Japanese fishnet manufacturer Nitto Seimo to develop the cord, which has been 10 years in the making.
"The tether uses our fishnet plaiting technology, but it was really tough to intertwine the very thin materials," company engineer Katsuya Suzuki told AFP.
"The length of the tether is 700m but eventually it's going to need to be 5000m to 10,000m long to slow down the targeted space junk,' he said.
A spokesman for the space agency said it hopes to put the junk collection system into more regular use by the middle of next decade.
"If we are successful in this trial, the next step will be another test attaching one tip of the tether to a targeted object," he said.
Yesterday's launch comes a week after a Russian shipment was destroyed shortly after lift-off.
The Russian rocket accident and the grounding of one of Nasa's commercial suppliers make this delivery all the more urgent. The spacecraft should arrive at the ISS on Tuesday.
The capsule, called Kounotori, or stork, also contained nearly 5 tonnes of food, water and other supplies including new lithium-ion batteries for the station's solar power system.
Astronauts will conduct spacewalks next month to replace the old nickel-hydrogen batteries that store energy generated by the station's big solar panels. SpaceX launches, meanwhile, have been on hold since a September rocket explosion on the pad in Florida.
