NEW YORK, Aug 28 (Reuters) - Plains All American Pipeline LP said trades at its own Midland crude terminal should be included in a key price assessment, responding to a proposal by Argus Media to remove it:
* Plains' 670,000 barrel-per-day (bpd) Cactus II pipeline began commercial deliveries earlier this month, sending WTI Midland prices at Plains' terminal as much as 50 cents per barrel above those at Enterprise's terminal, market sources said this week.
* The disconnect in prices prompted Argus Media to propose a change to its WTI Midland pricing methodology to exclusively reflect prices at Enterprise's terminal. The proposed change is open for comments until the end of the month.
* "Given the volume of physical activity at both the Enterprise and Plains terminals, Plains believes that it would be appropriate to include trades at both locations in order to more accurately capture the market price at Midland for each grade," Harry Pefanis, Plains All American Pipeline's president and chief commercial officer said in an emailed statement late on Tuesday.
* The Argus quotes for both WTI and West Texas Light (WTL) are used by a number of entities in the Midland markets, Pefanis said.
* Argus did not immediately respond to a request for comment. (Reporting by Devika Krishna Kumar in New York Editing by Marguerita Choy)