US Cash Crude-Coastal grades ease further on new tariff uncertainty

March 6 (Reuters) - U.S. coastal grades eased further on Thursday, dealers said, as market participants wrangled with uncertainty around U.S. tariffs on Mexico and China, the imposition of which drove spot prices for the grades higher earlier this week.

U.S. President Donald Trump exempted goods from Canada and Mexico under a North American trade pact for a month from the 25% tariffs that he imposed this week, the latest twist in fast-shifting trade policy that has whipsawed financial markets and business leaders.

A source familiar with the discussions said Trump could eliminate the 10% tariff on Canadian energy imports, such as crude oil and gasoline, that comply with existing trade agreements.

Trump's tariffs - a 10% tariff on Canadian oil and a 25% tariff on imports from Mexico - took effect overnight on Tuesday and were expected to force buyers to seek alternative supplies of heavier Canadian or Mexican crude, or pay higher prices.

Light Louisiana Sweet WTC-LLS eased 30 cents at a midpoint of a $3.75 premium to U.S. crude futures CLc1, while Mars Sour WTC-MRS eased 75 cents at a midpoint of a $1.60 premium.

Mars Sour had surged earlier this week, in one of the first indications that Trump's tariffs were disrupting the global oil trade.

In refinery news, Marathon MPC.N will begin planned maintenance activities on units at its 255,000-barrel-per-day refinery in Robinson, Illinois on March 18, a source familiar with plant operations said on Thursday.

Light Louisiana Sweet WTC-LLS for April delivery eased 30 cents at a midpoint of a $3.75 premium and was seen bid and offered between a $3.00 and $4.50 a barrel premium to U.S. crude futures CLc1

Mars Sour WTC-MRS eased 75 cents at a midpoint of a $1.6 premium and was seen bid and offered between a $1.50 and $1.7 a barrel premium to U.S. crude futures CLc1

WTI Midland WTC-WTM was little changed at a midpoint of a $1.15 premium and was seen bid and offered between a $1.05 and $1.25 a barrel premium to U.S. crude futures CLc1

West Texas Sour WTC-WTS was little changed at a midpoint of a 80-cent premium and was seen bid and offered between a 75-cent and 85-cent a barrel premium to U.S. crude futures CLc1

WTI at East Houston WTC-MEH, also known as MEH, traded between a $1.30 and $1.50 a barrel premium to U.S. crude futures CLc1

ICE Brent May futures LCOc1 rose 16 cents to settle at $69.46 a barrel

WTI April crude CLc1 futures rose 5 cents to settle at $66.36 a barrel

The Brent/WTI spread WTCLc1-LCOc1 widened to last trade at minus $3.48, after hitting a high of minus $3.33 and a low of minus $3.52