CNOOC, the state-owned Chinese energy company, was yesterday assessing how its chances of sealing a deal with California-based Unocal would be affected by a congressional move that would delay completion of a regulatory review of any takeover.

US lawmakers agreed late on Monday night that the committee on foreign investments in the US, an inter-agency panel that reviews foreign takeovers of US companies, would be barred from completing its inquiry into any CNOOC-Unocal deal until three government departments had finalised a study of the impact of China's energy demands on US security. The study, which must be completed within 120 days, would also investigate the level of reciprocity in US-China trade relations.