US Cash Crude-Grades mixed as traders return from long holiday weekend

May 27 (Reuters) - U.S. cash crude grades were mixed on Tuesday, dealers said, as traders came back after a long holiday weekend and adjusted following the end of a three-day roll trading period.

The roll period ended on Friday. Traders use the three-day roll trade to square positions and manage exposure, and trading tends to be volatile.

Traders returned on Tuesday from the Memorial Day holiday weekend. It marks the unofficial start of summer in the U.S., when driving - and demand for gasoline - usually rises.

Light Louisiana Sweet WTC-LLS for July delivery weakened 30 cents at a midpoint of a $2 premium, while WTI Midland WTC-WTM, another sweet grade, was little changed at a midpoint of a 65-cent premium.

Mars Sour WTC-MRS strengthened 35 cents at a midpoint of a 50-cent premium and West Texas Sour WTC-WTS weakened to a midpoint of parity.

U.S. crude's discount to the international benchmark Brent WTCLc1-LCOc1 narrowed on Tuesday, making U.S. crude grades less attractive to foreign buyers.

In oil futures, prices settled 1% lower as investors worried about a supply glut after Iranian and U.S. delegations made progress in their talks and on expectations that OPEC+ will decide to increase output at a meeting this week. O/R

* Light Louisiana Sweet WTC-LLS for July delivery weakened 30 cents at a midpoint of a $2 premium and was seen bid and offered between a $1.90 and $2.10 a barrel premium to U.S. crude futures CLc1

* Mars Sour WTC-MRS strengthened 35 cents at a midpoint of a 50-cent premium and was seen bid and offered between a 40-cent and 60-cent a barrel premium to U.S. crude futures CLc1

* WTI Midland WTC-WTM was little changed at a midpoint of a 65-cent premium and was seen bid and offered between a 55-cent and 75-cent a barrel premium to U.S. crude futures CLc1

* West Texas Sour WTC-WTS weakened to a midpoint of parity and was seen bid and offered between a discount of 20 cents and a 20-cent a barrel premium to U.S. crude futures CLc1

* WTI at East Houston WTC-MEH, also known as MEH, traded between a 60-cent and $1 a barrel premium to U.S. crude futures CLc1

* ICE Brent July futures LCOc1 fell 65 cents to settle at $64.09 a barrel

* WTI July crude CLc1 futures fell 64 cents to settle at $60.89 a barrel

* The Brent/WTI spread WTCLc1-LCOc1 narrowed to last trade at minus $3.19, after hitting a high of minus $3.17 and a low of minus $3.28.