Construction launched on 3,968 kilometre 'Power of Siberia' gas pipeline.
Altai route for gas to China could take priority, reported Reuters.
Beijing reviewing its energy needs with slowing economy, says report.
Agreement means Power of Siberia pipe could be delayed, it is claimed.
New field will enable eventual exports to China via 'western route' through Altai Mountains.
Dignitaries gather on Chinese side of the pipeline to witness the formal welding of the first joint in $55billion line.
Supplies to EU maintained despite mega-blast with flames 200 metres in the sky, and heat felt 1km from fireball.
Gazprom says operations are 'in full swing' with work due to start soon on iconic pipeline to provide gas on eastern route.
Gazprom subsidiary Tomskgazprom has announced the terminal to produce propane and butane mixtures.
After months of speculation, parliament and President rubber-stamp deal that will see gas sent to China.