After rising above $100 on Thursday, Brent was up 0.20 percent at $100.66 by about 0020 GMT, while West Texas Intermediate was flat at $95.75.
In Japan, the Nikkei was down 1.4 percent at 53,687.30 points, while in South Korea, the Kospi was down 2.2 percent at 5,462.97.
With Gulf states cutting production and oil tankers stranded in the Gulf, benchmark oil prices have risen 40 to 50 percent since the United States and Israel attacked Iran on February 28, threatening to curb growth and curb inflation.
The Strait of Hormuz, a critical waterway for crude, remains effectively closed.
Saudi forces intercepted dozens of drones on Friday and Israel came under a missile attack launched by Tehran.
The International Energy Agency has warned that a Middle East war could lead to the “biggest supply disruption” in the industry’s history.
But US President Donald Trump wrote on social media that defeating Iran’s “evil empire” was more important than crude oil prices.
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