London - Oil prices fell slightly on Friday as traders awaited the outcome of talks over Greece's bailout and Iran's nuclear programme.
US benchmark West Texas Intermediate for delivery in August slipped 22 cents to $59.48 a barrel compared with Thursday's close.
Brent North Sea crude for August dipped 2c to stand at $63.18 a barrel in London afternoon deals.
Crude futures were weighed down over the week meanwhile by high levels of supplies in the United States, the world's biggest consumer of oil.
"The focus for Friday and into the weekend will be on Greece," said Singapore's United Overseas Bank.
Crude investors were weighing the "potential negative impact from Greece's debt crisis on European energy demand", the lender said in a market commentary.
Dealers are also keeping a close watch as Iran and major Western powers race to agree a deal by June 30 that would see Tehran open up its nuclear programme to allay concerns it is seeking atomic weapons, in return for the West lifting punishing economic sanctions.
Any agreement could result in Iranian crude returning to the world market, adding to the current oversupply which sent prices plunging from more than $100 a barrel last year.