Oil prices are approaching last year’s highs as tensions increase over Iran’s nuclear program. The rise pushed gasoline prices on Friday to a national average of $3.65 per gallon, the highest ever for this time of year.

Western nations fear Iran is building a weapon and have been trying to force it to open its facilities to inspection. Iran has refused, turning away international inspectors this week for the second time this month.

As tensions rise, investors are snapping up oil contracts in anticipation of a protracted standoff with one of the world’s top oil explorers.

Benchmark West Texas Intermediate crude rose 40 cents to $108.23 per barrel in New York. Brent crude rose 22 cents to $123.84 per barrel in London.

WTI peaked near $114 a barrel last May.