The disparity between the Brent and West Texas Intermediate oil exchange traded is growing, with the spread widening to an eight month high, as stalling Iran nuclear talks bolstered Brent and the U.S. oil boom weighs on WTI.

The United States Brent Oil Fund (NYSEArca: BNO), which tracks Brent crude, gained 0.8% Friday while the United States Oil Fund (NYSEArca: USO), which tracks front-month West Texas Intermediate crude oil, was down 0.4%. Over the past three months, BNO was 2.7% higher, compared to the 8.1% decline in USO.

Brent crude oil futures were hovering around $111 per barrel Friday while WTI crude traded at $94.9 per barrel.

The spread widened to over $16 from $14.64 Thursday, with Brent hitting a five-week high as talks over Iran’s nuclear program stalled, reports Moming Zhou for Bloomberg.

Iran’s oil exports have been reduced by sanctions. Any failure in the talks increases the likelihood of additional sanctions from the U.S. [Brent ETF: The Better Oil Futures Play]

“Things could get worse in Iran and it’s going to be supportive for Brent,” Phil Flynn, senior market analyst at the Price Futures Group, said in the article. “WTI is having a hard time moving higher because there is so much supply.”