The launch of a key module of the International Space Station (ISS) has been delayed yet again after flaws were detected in a booster rocket, a top Russian space official said on Tuesday.

Sergei Gromov, spokesman for the Energia Company which built the module, said the launch of Zvezda will not be possible until at least August.

The launch had already been delayed 18 months, causing major hold-ups for the whole project.

Nasa spokesman Duane Brown said that if there is a significant change, the US agency will look at having a space shuttle mission go up to the space station to do some housekeeping.

"We, as an agency, certainly applaud the Russians and we are awaiting a meeting, sometime in February, when they will give an official launch date for the service module," he said.

Faulty parts

Mr Gromov said the delay was necessary after engineers detected faults in the manufacture of the Proton booster rocket, which is to put Zvezda into orbit. The rocket manufacturer must replace faulty parts and this is expected to be done by the end of June.

"Once the booster is ready, it takes about 45 days to prepare the module for launch, so the earliest launch time is the end of August," he added.

Mr Gromov also said that some software problems with Zvezda's computers had to be resolved before launch: "Obviously, the Americans are not pleased with the delay, but they react with understanding."

The Zvezda module is crucial because it will steer the entire $60bn dollar station and provide oxygen and living facilities for the first crew.

Russian officials began an investigation after two Proton rockets crashed shortly after launch on 5 July and 27 October 1999. The failures sent debris raining down on Kazakhstan.

Moonlighting

According to the news agency Interfax, investigators determined on Tuesday that metal dust particles contaminated the second-stage engines. The engines for both the failed Protons came from the same batch produced in 1992 by the Voronezh Mechanical Works.

The problem, says Interfax, may have arisen because Voronezh Mechanical Works used its factory to produce commercial goods and in the process damaged precision rocket equipment.

State financing for Russian space factories is tiny, often forcing managers to look for alternative income sources.