UPDATE 4-Brent falls below $110, on track for highest weekly close in '14

* South Sudan cuts oil output to 170,000 bpd

* China and India boost imports of Iranian crude

* Coming up: U.S. existing home sales at 1500 GMT

(Updates prices, details)

LONDON, Feb 21 (Reuters) - Brent crude oil slipped below $110 a barrel on Friday but remained on course for its highest weekly close this year, as supply disruptions in Africa have tightened the market.

U.S. benchmark West Texas Intermediate was heading for its sixth straight weekly rise and its discount to Brent has shrunk to the narrowest in four months, as a new pipeline helps drain supplies from WTI's delivery point at Cushing, Oklahoma.

Prices faced some pressure on signs Iran substantially increased crude oil exports to China and India in January, though total exports from the Islamic Republic remain constrained by Western sanctions.

The United Nations atomic watchdog also reported on Thursday that Iran's most contested uranium stockpile has declined significantly following a landmark nuclear deal with world powers in November.

Brent for April delivery was down 21 cents at $110.09 a barrel by 1208 GMT, having hit a seven-week high of $110.82 on Wednesday. Its low on Friday was $109.90.

U.S. crude futures for April delivery dropped 25 cents to $102.50, and touched a low of $102.34.

Brent's premium to U.S. crude <CL-LCO1=R> narrowed to as little as $7.09 in the previous session, its tightest since Oct. 9, and was around $7.50 a barrel on Friday.

Data from the U.S. Energy Information Administration on Thursday was mixed for oil as Cushing crude stocks fell 1.73 million barrels in the week to Feb. 14, while the country's overall crude inventories rose almost 1 million barrels.

"The market is very focused on Cushing, but stocks are flowing to the Gulf Coast where they're starting to build up," said Harry Tchilinguirian, head of commodity markets strategy at BNP Paribas in London.

Crude stockpiles in Cushing have fallen below the five-year average, but the recent rate of inventory declines was unlikely to be sustained due to a rise in domestic production, Tchilinguirian said. Seasonal refinery maintenance in March and April will also reduce demand, he added.

A weaker U.S. dollar, which fell to a seven-week low against the euro earlier this week, has boosted demand for dollar-denominated commodities as they become more affordable to holders of other currencies.

Domestic conflicts in Libya and South Sudan, and escalating protests in Venezuela have added support to Brent prices.

South Sudan's oil production has fallen by about a third to around 170,000 barrels per day (bpd), as the capital of the main oil-producing region has been divided by the army and rebel fighters.

Maintenance at Angola's Plutonio oilfield in March will also cut supply by about 180,000 bpd.

Libya's oil output is just less than a quarter of its pre-Arab Spring levels, languishing below 400,000 bpd.

Traders also eyed the turmoil in Ukraine, where violence escalated sharply on Thursday between pro-European protesters and forces loyal to Russian-backed President Viktor Yanukovich.

Yanukovich on Friday announced plans to hold early presidential elections, form a national unity government and make constitutional changes reducing his powers. The violence has strained ties between Moscow and members of the European Union, a major market for Russian oil and gas.

(Additional reporting by Florence Tan in Singapore; Editing by Dale Hudson)