Brent oil futures slipped below $110 per barrel on Friday, but were on track to end higher for the second straight week following sharp overnight gains, with investors waiting for the outcome of talks on Iran's nuclear programme.

Oil prices jumped on Thursday, fuelled by a sharp run in gasoline, signs of continued economic strength in the United States and signs that a deal to curb Tehran's nuclear programme could be a long time coming.

Brent for January delivery was down 14 cents at $109.94 per barrel at 0310 GMT. US crude was trading 24 cents lower at $95.20 per barrel, after posting its biggest gain in nearly two months on Thursday.

The US benchmark was driven higher in part by New York gasoline futures, which surged on supply concerns as an outage at the nation's largest refinery added to a cluster of plant problems.

Iran and six major powers have made some progress this week towards an interim deal, but negotiators appeared to downplay anticipation of an imminent breakthrough in the three-day talks that began on Wednesday.

Prior to the meeting, expectations of a breakthrough had remained high after the United States, Russia, China, France, Britain and Germany came close to winning concessions from Iran in the last round of negotiations two weeks ago.

"What is coming out the talks now is what many had expected. It is going to take months or maybe even years before we get anything concrete out of this," said Tony Nunan, oil risk manager at Mitsubishi Corp in Tokyo.

"From the beginning, Iran has insisted on the right to enrichment for power generation, and they are certainly not just going to roll over on that."

Adding to pressure on negotiators, US Senate Majority Leader Harry Reid said on Thursday he was committed to moving ahead with a tougher Iran sanctions bill. - Reuters