U.S. Oil prices hit nearly six month highs on Tuesday, continuing to rally after U.S. President Donald Trump surprised the market with strict new measures aimed at driving Iran’s crude exports to zero.

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The Trump administration announced on Monday that it will not extend sanctions waivers to a handful of countries that import Iranian oil. The decision means any entity caught purchasing Iran’s barrels after May 1 risks triggering U.S. sanctions, which are designed to deprive the Iranian leadership of oil revenue.

U.S. West Texas Intermediate crude settled 75 cents higher at $66.30 a barrel, rising 1.1% and setting a new closing high going back to Oct. 29. WTI earlier rose as high as $66.60 on Tuesday, its best intraday price since Oct. 31.