HOUSTON - Lyondell Chemical Co. announced an agreement in principle to acquire Occidental Petroleum Corp.'s 29.5% stake in Equistar Chemicals LP. The transaction would bring Lyondell's ownership interest in Equistar to 70.5%. Millennium Chemicals Inc. holds the remaining 29.5% stake.

Equistar Chemicals was formed in 1997 with the combination of the olefins and polymers businesses of Lyondell and Millennium. Occidental joined the partnership in 1998 with the contribution of the ethylene, propylene, ethylene oxide and derivatives businesses of its Occidental Chemical Corp. subsidiary.