Oil prices traded flat Friday in a market still devoid of strong demand or supply signals but wary of Greece's cliffhanger debt talks and negotiations about Iran's nuclear program in Vienna.

On the New York Mercantile Exchange, West Texas Intermediate (WTI) or light sweet crude for August stood at $59.63 a barrel, down seven cents from Thursday, and 23 cents above where the price stood a week ago.

On London's Intercontinental Exchange, Brent North Sea crude for delivery in August added 6 cents for the day to $63.26 per barrel, up 60 cents from a week before.

"The market has looked apathetic and somewhat tired, so we're seeing a bit of short-covering ahead of the weekend," said Matt Smith of Clipper Data.

"The sentiment on Greece is ebbing and flowing," he noted, as pressure mounted on Friday for Athens to accept what appeared to be the final European proposal of conditions for funding.

Greece desperately needs more bailout money to make a 1.5 billion euro ($1.7 billion) debt payment to the IMF by Tuesday, but has repeatedly rejected certain reforms demanded by creditors.

"If there's a resolution, it's going to be positive for the euro, ergo for the crude market," said Smith.

The market is also waiting to see if Iran and major world powers can reach a deal on curbing Tehran's nuclear program by the end of the month that would allow Western powers to remove sanctions, opening the spigots for more Iranian crude to hit the international market.

Efforts to finalize a pact remain stuck on several issues, diplomats from both sides said Friday as US Secretary of State John Kerry headed to Vienna for weekend talks.