March 4 (Reuters) - U.S. coastal grades strengthened on Tuesday, after the U.S. imposed a 10% tariff on Canadian oil and a 25% tariff on imports from Mexico.

The tariffs, which took effect overnight on Tuesday, were expected to force buyers to seek alternate supplies of heavier Canadian or Mexican crude, or pay higher prices.

Mars Sour WTC-MRS firmed 50 cents at a midpoint of a $2.75 premium to U.S. crude futures CLc1, the strongest level since December. During the session, it climbed to as high as a $3.60 per barrel premium, a 60% increase from the last trade on Monday.

Light Louisiana Sweet WTC-LLS firmed 55 cents at a midpoint of a $4.45 premium, the strongest since November 2022, though dealers did not see it trade.

One trader said Tuesday's market indicated some panic-buying, as dealers had been waiting to see if President Donald Trump would move forward with the tariffs.

In other energy news, the Trump administration said on Tuesday it was ending a license that the U.S. had granted to oil producer Chevron CVX.N since 2022 to operate in Venezuela and export its oil, after Washington accused President Nicolas Maduro of not making progress on electoral reforms and migrant returns.

* Light Louisiana Sweet WTC-LLS for April delivery firmed 55 cents at a midpoint of a $4.45 premium and was seen bid and offered between a $3.90 and $5.00 a barrel premium to U.S. crude futures CLc1

* Mars Sour WTC-MRS firmed 50 cents at a midpoint of a $2.75 premium and was seen bid and offered between a $2.65 and $2.85 a barrel premium to U.S. crude futures CLc1

* WTI Midland WTC-WTM eased 5 cents at a midpoint of a $1.05 premium and was seen bid and offered between a 95-cent and $1.15 a barrel premium to U.S. crude futures CLc1

* West Texas Sour WTC-WTS firmed 5 cents at a midpoint of a 75-cent premium and was seen bid and offered between a 65-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 $1.20 and $1.40 a barrel premium to U.S. crude futures CLc1

* ICE Brent May futures LCOc1 fell 58 cents to settle at $71.04 a barrel

* WTI April crude CLc1 futures fell 11 cents to settle at $68.26 a barrel

* The Brent/WTI spread WTCLc1-LCOc1 narrowed to last trade at minus $3.35, after hitting a high of minus $3.31 and a low of minus $3.46

(Reporting by Stephanie Kelly in New York; Editing by Alan Barona)

((Stephanie.Kelly@tr.com))