April 5 (Reuters) - The differential of Western Canada

Select (WCS) heavy crude versus the North American benchmark

West Texas Intermediate (WTI) widened on Friday.

* WCS for May delivery in Hardisty, Alberta, began trading

at $12.85 per barrel below WTI and ended at $13 under, according

to brokerage CalRock. On Thursday, May WCS traded between $12.40

and $12.60 below WTI.}

* Trans Mountain said Wednesday its expanded oil

pipeline would start operating on May 1.

* The pipeline's progress and line fill ahead of its opening

had driven the differential narrower but some market

participants are now turning cautious about the logistics of

smoothly loading oil from the expanded pipeline to vessels in

British Columbia, an industry source said.

* Brent crude LCOc1 climbed more than $1 a barrel as markets

watched for a possible direct conflict between Israel and Iran.