Saudi Aramco is reviewing its $9 billion Manifa oilfield project and Saipem, a major contractor, has been told not to take on any more commitments for it, the Italian company said.

The review involving the 900,000 barrels per day offshore project is another sign Aramco, by far the world's biggest oil company by output, wants to renegotiate contracts it signed at the height of the commodities price boom.

Saipem, one of Europe's biggest oilfield services companies, did not specify in a statement whether other suppliers or contractors were affected.

Saipem said it still had its contract for onshore development. Shares in Saipem, one of Europe's biggest oil services companies, plunged on rumours it had lost the contract.

However, Aramco has directed that no further commitments towards suppliers and contractors be taken on pending an analysis 'aimed at cost optimisation', Saipem said.

Shares in Spain's Tecnicas Reunidas, which according to its website is also a contractor on the project, gave up gains of five per cent yesteday to close down more than 6pc.

The Aramco move is an important sign oil companies are gaining bargaining power as lower oil prices ease the urgency to invest in projects, a Milan analyst said.

'Oil companies can now afford to review contracts that have already been closed. It's a precedent,' said the analyst.

Khalid Buraik, Saudi Aramco's executive director of affairs, said earlier Saudi Arabia may renegotiate contracts for long-term projects as falling oil prices and the credit crunch ease competition for resources and so bring down project costs.