Oil prices extended losses on Friday and headed for a weekly decline as the prospect of an increase in Iranian oil exports outweighed fears of possible supply disruptions from the Russia-Ukraine crisis.
Brent crude futures fell $2.44, or 2.6 percent, to $90.53 a barrel, after ending trading on Thursday, down 1.9 percent.
US West Texas Intermediate crude fell $2.39, or 2.6 percent, to $89.37 a barrel, after closing down 2 percent in the previous session.
Fears of possible supply disruptions as a result of the Russian military build-up on the Ukrainian border limited losses this week.
Both benchmark contracts reached their highest levels since September 2014 on Monday, but the prospect of easing oil sanctions on Iran set prices on course for their first weekly decline in nine weeks.
But diplomats say an agreement on reviving the 2015 Iran nuclear deal with world powers sets out stages of joint steps to bring the two sides back into full compliance, and the first stage may not include waivers from oil sanctions.
Therefore, analysts say that there is little chance of Iranian crude returning to the market in the near future to ease the current supply shortage.