* Brent futures set to end year below $111
* Traded between $96.75 and $119.17 in 2013
* U.S. crude traded between $85.61 and $112.24
* Libya's oil export ports still shut as deadlock drags on
(Recasts with price drop, adds comment)
LONDON, Dec 31 (Reuters) - Brent crude oil slipped below $111 a barrel on Tuesday on optimism of increased exports from Libya and South Sudan as the European benchmark looked set to end slightly down for the year.
Concerns about supply disruptions in the Middle East and Africa have partially offset concerns about weak global demand in 2013 after four years of gains in Brent.
It has traded in a $22 range from $96.75 to $119.17 a barrel this year.
U.S. oil was on track to end more than 7 percent higher for 2013, recouping a 7 percent loss last year and giving it gains in four of the past five years.
The spread between Brent crude oil futures and those for U.S. oil was on course to narrow by $7 a barrel for the year, Reuters data showed.
In light trade, Brent crude was down 37 cents to $110.84 a barrel by 1330 GMT, slightly below 2012's closing price of $111.11. U.S. oil was down 73 cents to $98.56.
"There's been some optimism about the potential return of supplies from South Sudan and Libya, and that's probably what's helped Brent down," said Amrita Sen, chief analyst at consultants Energy Aspects.
Violence in South Sudan has reduced crude oil output by about a fifth to 200,000 barrels per day (bpd) in the world's youngest country, but a possible end was in sight with South Sudan's government and rebels sending delegates to peace talks in Ethiopia on Tuesday.
In Libya, where protests have slashed output to less than 250,000 bpd from 1.4 million bpd in July, the Sarir and Messla oilfields are up and running. But the Hariga oil port they connect with, which officials had said was to open soon, needs to reopen before exports can resume.
Vienna-based consultancy JBC Energy was pessimistic, however, about Libyan oil output for the year ahead.
"In our best case, we estimate Libyan production could return to capacity in May, however we actually believe the country will not produce more than 1 million bpd on a monthly average in 2014," a JBC Energy report said.
Growing unrest in crude exporter Iraq, tensions between Iran and the West over Tehran's disputed nuclear programme, and the recent outages in Libya have helped support oil prices this year.
These factors have offset concerns over a weak demand outlook in industrialised nations and a slowdown in consumption in China, the world's second-biggest oil consumer.
"As we move into 2014, markets are once again trying to balance various supply disruptions with some positive news," the JBC Energy report said.
Violence in Iraq increased this year as al Qaeda-linked militants target the government and anyone seen to be supporting it, keeping investors worried about a disruption in shipments from the country.
Talks are ongoing between Iran and world powers on how to roll out last month's breakthrough deal in the dispute over the Islamic Republic's nuclear programme, but the OPEC member's exports have fallen by more than half to 1 million bpd due to sanctions imposed by the West.
A drawdown of stockpiles in the United States has helped to ease concerns of a supply glut in the world's largest oil consumer and boosted U.S. oil in 2013.
In the year ahead, investors are watching for further developments in the U.S. Federal Reserve's scaling back of its monetary stimulus.
While the tapering suggests the world's biggest economy is gaining steam, it will also reduce the availability of the dollar, weighing on oil and other commodities priced in the currency.
(Additional reporting by Manash Goswami in Singapore; Editing by Angus MacSwan)