Oil prices rose on Friday amid tensions over the Ukraine crisis, as traders braced for a weekend vote in its Crimea region on whether to join Russia. Brent North Sea crude for delivery in April shot up $1.18 to $108.57 in London trade. New York's main contract, West Texas Intermediate for April, closed 69 cents higher at $98.89 a barrel. "The prospect of increasing animosity between the West and Russia is lending some support to crude ahead of the weekend," said Matt Smith of Schneider Electric. Top Russian and US diplomats failed Friday to defuse the crisis over Ukraine, ending up at loggerheads following tense talks over the worst East-West clash since the Cold War. Oil markets have been relatively calm despite the standoff over Ukraine since February 22, when street protests ended up ousting Ukraine's pro-Kremlin president Viktor Yanukovych. Since then, Russian troops have seized control of predominantly ethnic-Russian Crimea, and Moscow has promoted the referendum on Sunday to decide if it will join Russia or remain in Ukraine. Investors worried that potential Western sanctions against Russia could disrupt oil and gas supplies from the country. More than 70 percent of its gas and oil exports to Europe pass through Ukraine. Traders "don't want to be caught short before the weekend in case something happens," said Phil Flynn of Price Futures Group. Oil traders also weighed a brighter outlook on global demand from the International Energy Agency. The IEA on Friday raised its 2014 world demand estimate by 95,000 barrels to 92.7 million barrels per day. "Growth momentum is expected to benefit from a more robust global economic backdrop," the IEA said, raising its estimate for the fourth consecutive month. "The pace of growth will likely build through the year, as underlying macroeconomic conditions improve, but the standoff in Ukraine has increased downside risk to the forecast," it added.