Oil prices rose in Asia Friday but gains were capped as dealers eyed the deadlocked Greek debt talks expected to come to a head over the weekend, analysts said.

US benchmark West Texas Intermediate for August delivery gained 10 cents to $59.80 while Brent crude for August gained 38 cents to $63.58 in afternoon trade.

"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.

Greece's emergency negotiations with its creditors -- the European Union and the International Monetary Fund -- ended abruptly Thursday, pushing the crisis toward a critical weekend meeting in a bid to avoid a default by Athens and its potential exit from the eurozone.

Talks will resume on Saturday, just days before the June 30 deadline for Greece to make a 1.5 billion euro payment to the IMF, and the day its EU bailout will expire.

German Chancellor Angela Merkel said the Saturday meeting would be "decisive" for finding a debt deal for Greece.

"We have to keep working because time is pressing and the Eurogroup on Saturday will have a decisive importance," Merkel told a news conference early Friday at an EU summit in Brussels.

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.

A top US official who did not want to be named told reporters Thursday the deal could "slip" by a few days past the June 30 deadline.