July 25 (Reuters) - Cash price differentials for coastal U.S. crude grades weakened on Friday, dealers said, on the final day of the roll trade period.

The three-day roll trade period begins on the session after the expiration of the front-month U.S. crude futures contract CLc1. Traders use it to square positions.

Coastal grades Light Louisiana Sweet WTC-LLS and Mars Sour WTC-MRS weakened on Friday despite indications of tightening U.S. supplies.

U.S. energy firms this week cut the number of oil rigs by seven to 415 this week, their lowest since September 2021, energy services firm Baker Hughes BKR.O said.

Oil futures eased to settle at a three-week low as traders worried about negative economic news from the U.S. and China and signs of growing supply. O/R

U.S. oil refiners are expected to have about 171,000 barrels per day of capacity offline in the week ending July 25, increasing available refining capacity by 74,000 bpd, research company IIR Energy said.

* Light Louisiana Sweet WTC-LLS for August delivery weakened $1.60 at a midpoint of a $1.00 premium and was seen bid and offered between a 90-cent and $1.10 a barrel premium to U.S. crude futures

* Mars Sour WTC-MRS weakened 10 cents at a midpoint of a $1.2 discount and was seen bid and offered between a $1.30 and $1.10 discount to U.S. crude futures

* WTI Midland WTC-WTM strengthened 5 cents at a midpoint of a 10-cent premium and was seen bid and offered between parity and 20-cent premium to U.S. crude futures

* West Texas Sour WTC-WTS was little changed at a midpoint of a 70-cent discount and was seen bid and offered between a 90-cent and 50-cent discount to U.S. crude futures

* WTI at East Houston WTC-MEH, also known as MEH, traded between a 50-cent and 70-cent premium to U.S. crude futures

* ICE Brent September futures LCOc1 fell 74 cents to settle at $68.44 a barrel

* West Texas Intermediate September crude CLc1 futures fell 87 cents to settle at $65.16 a barrel

* The Brent/WTI spread WTCLc1-LCOc1 widened to last trade at minus $3.26, after hitting a high of minus $3.12 and a low of minus $3.28

(Reporting by Stephanie Kelly in New YorkEditing by Marguerita Choy)

((Stephanie.Kelly@tr.com))