Oil prices slipped on Friday as a strong dollar and recent gains incentivised investors to cash in, while focus shifted again to swelling global inventories that have cushioned the impact from unplanned supply outages.

Global benchmark Brent crude prices traded down 30 cents at $48.51 a barrel at 1404 GMT.

U.S. West Texas Intermediate (WTI) crude futures traded at $47.91 a barrel, down 25 cents day on the day.

The dollar was on course for a third straight weekly gain on Friday on hints the United States is getting closer to raising interest rates.

A stronger dollar makes it more expensive for investors to hold greenback-denominated commodities like oil futures.

"Despite supply disruptions, there is still oversupply and large inventories. Investors have probably shifted focus," said Hans van Cleef, senior energy economist at ABN AMRO in Amsterdam.

Russian Energy Minister Alexander Novak said he saw supply in excess of demand of around 1.5 million barrels per day (bpd).

He also poured cold water on expectations of the outcome of the next meeting of OPEC members on June 2, saying they were unlikely to make a decision on coordinated action to prop up the oil market.

Oil prices had been supported in recent days by growing supply disruptions in oil producing countries like Nigeria, Canada and Libya.

In Nigeria, militant activity has cut oil exports to a more than 22-year low of under 1.4 million bpd.

In Canada, production has also been cut as wildfires forced closures of around 1 million barrels in daily production, although output is gradually returning.

Libyan output has also been hit by internal conflict.

Some analysts said they expected oil prices to come further off recent highs, correcting their recent upwards trend.

"We feel that markets have moved too high, too far, too soon," Harry Tchilinguirian, lead oil and commodities strategist at French bank BNP Paribas in London, told Reuters' Global Oil Forum.

"The combination of a stronger dollar, still excess supply over demand and ongoing overhang of inventories can be expected to put strong downward pressure on prices."

He said oil prices could fall to the mid to high $30-a-barrel range.-Reuters