An unmanned Russian cargo spacecraft ferrying supplies to the International Space Station is said to be plunging back to Earth and is apparently out of control.
"It has started descending. It has nowhere else to go," an official familiar with the situation said on condition of anonymity.
An official Russian space agency statement is expected later in the day.
"It is clear that absolutely uncontrollable reactions have begun."
Russian flight controllers had been trying to re-establish contact with the craft.
The Progress 59 cargo spacecraft launched successfully on a Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan yesterday and was due to dock with the ISS six hours later.
The early part of the flight went without difficulty but an unspecified problem arose soon after the craft separated from the third stage.
Tumbling to Earth - Mission Control Moscow has had no luck contacting the Progress. It'll now slowly fall & burn up. pic.twitter.com/lbkJZq36bM
— Chris Hadfield (@Cmdr_Hadfield) April 29, 2015According to NASA the issue prevented flight controllers from confirming if two of the craft's antennae had deployed successfully or not.
As a result they decided to opt for a backup rendezvous plan which would see the cargo arrive at the ISS after two days rather than the six hours.
Several attempts were subsequently made to re-establish contact with the craft during the following orbits of Earth, but without success.
The docking attempt planned for tomorrow has also been stood down.
NASA says the six crew on board the ISS are all fine and the station itself is also safe.
The crew have sufficient supplies to last several months.
The Progress 59 was not carrying any mission critical supplies, but it did have over three tonnes of food, water, propellant, oxygen, parts and other supplies on board.
If the flight controllers are unable to get control of the craft it will most likely drop out of orbit and burn up in the Earth's atmosphere in the next few days.
Only the US, Russia and Japan carry out resupply missions to the ISS after the European Space Agency completed its final delivery mission earlier this year.
SpaceX and Orbital Sciences are contracted by NASA to do the US deliveries, but Orbital Sciences craft are currently grounded following a launch explosion last October.
The next planned resupply mission will be carried out by SpaceX in June. The following one will be run by Japan in August.
An engine mishap on a similar Progress flight in 2011 led to a complete loss of communication and a failure to reach the target orbit.
A few weeks later it crashed into Siberia in one of Russia's biggest space setbacks.
Three or four Progress cargo ships are launched every year bringing necessities like oxygen, fuel and food supplies to the orbiting laboratory.
After completing their mission they usually fall into the Pacific Ocean.
