Unexpected weather conditions on the Sun mean Russia's Mir space station will not be destroyed until some time between 13 and 18 March, perhaps even later, Russian officials say.

The station is taking longer than expected to fall to an altitude where the final ditching procedure can begin, a Russian space agency spokesman said on Thursday.

The delay has been caused by a flare-up in solar activity, which has made the Earth's atmosphere denser.

At the moment Mir is 280km (170 miles) above the Earth and falling at about 900 metres (3000 feet) a day.

It needs to fall to between 200 and 240 km (125 and 150 miles) for the final ditching manoeuvre to start, he said.

Russian controllers will make a more detailed prediction of Mir's final re-entry date once the 130-tonne laboratory reaches an altitude of 250 km (155 miles).

Staying power

Mir has a history of unexpected longevity.

When it was launched in 1986, it was designed to last three years.

Fifteen years later, it has been the venue for a series of space endurance records, including the longest space walk and the longest stay by an astronaut or cosmonaut in space.

A demonstration in Moscow saw Russians calling for it to stay in orbit as a symbol of national pride.

The Russian Government decided late last year to bring the platform down.

It will disintegrate and burn up as it tumbles through the thicker layers of the Earth's atmosphere.

Large chunks are expected to make it through to the surface of the planet, but Russian space officials hope to time the whole procedure so that any debris hits a remote area of the southern Pacific.