UPDATE 1-Phillips 66 offers to buy pipeline operator DCP Midstream

(Adds details on offer, background)

By Arathy Somasekhar

HOUSTON, Aug 17 (Reuters) - U.S. refiner Phillips 66 on Wednesday offered to acquire the public units of DCP Midstream in a deal that would value the pipeline operator at $7.2 billion deal and bulk up Phillip's natural gas liquids business.

A deal would mark the first major move by Mark Lashier, who took over as the chief executive officer of Phillips 66 last month. Earlier this year, the company acquired the public units in transportation and storage business Phillips 66 Partners.

Canadian pipeline operator Enbridge, which owned 50% of DCP's general partner, said it would reduce its stake in the company to 13.2% from 28.3%. It received a $400 million cash payment from Phillips 66 as part of the deal.

Enbridge will, in turn, take over as operator and more than double its stake in Grey Oak pipeline, previously operated by Phillips 66. The Grey Oak pipeline transport crude oil from West Texas to the Gulf Coast.

Phillips 66's economic interest in the Gray Oak pipeline will fall to 6.50% from 42.25%.

(Reporting by Arathy Somasekhar in Houston; editing by Gary McWilliams and Diane Craft)