The U.S. Congress passed a new package of sanctions against Iran that aims to punish banks, insurance companies and shippers that help Tehran sell its oil.
This builds on oil trade sanctions signed into law in December that prompted buyers in Japan, South Korea, India and other nations to slash their purchases of Iranian oil.
Brent crude gained 73 cents to $106.63 per barrel by 0633 GMT. U.S. oil rose 70 cents to $87.83, on track for its second weekly loss.
"The fighting in Syria, tensions in Iran, the North Sea maintenance plan and reduced OPEC daily supply are all coming together and providing support to Brent (prices)," said Nick Trevethan, senior commodities strategist at ANZ Bank in Singapore.
Maintenance work in the British sector of the North Sea will cut crude oil production in September.
The Brent contract is based on four North Sea crude oils --Brent, Forties, Oseberg and Ekofisk -- and export programs for September were expected to show a sharp drop.
Seaborne oil exports from OPEC, excluding Angola and Ecuador, will fall by 120,000 barrels per day in the four weeks to August 18, UK consultancy Oil Movements said.
KURDISTAN PLAN TO HALT EXPORTS
Adding to supply uncertainty, Iraq's semi-autonomous region of Kurdistan plans to halt oil exports on August 31 if the central government does not make all outstanding payments, the region's minister of natural resources said.
Middle East tension increased, with former U.N. Secretary-General Kofi Annan quitting as international peace envoy for Syria, frustrated by "finger-pointing" at the United Nations, while the armed rebellion against President Bashar al-Assad becomes increasingly bloody.
Also providing support, U.S. crude oil stockpiles last week fell by their most since December, while crude imports dropped and oil products also posted unexpected declines, federal government data showed on Wednesday.
Domestic stocks of crude, excluding oil held in the Strategic Petroleum Reserve, fell 6.52 million barrels to 373.59 million barrels in the week to July 27, the Energy Information Administration reported. Analysts polled by Reuters had forecast a much smaller drop of 700,000 barrels.
Disappointment that the European Central Bank did not offer more immediate steps to boost economic growth, and weak data from the U.S. and China, capped oil price gains.
The ECB, after keeping interest rates steady, indicated it might resume buying government bonds to drive down surging Spanish and Italian borrowing costs, but passed the baton back to euro zone governments by saying they must act first, disappointing markets.
Asian shares and the euro fell as a result.
"While action from the ECB will still likely happen in coming months, financial markets are not known for their patience and the lack of immediate action was inevitably met with some petulance by traders," Tim Waterer, senior trader at CMC Markets, wrote in a note on Friday.
Investors also have reason to be more cautious ahead of key U.S. non-farm payrolls data for July due at 1230 GMT. [ID:nL4E8J218U]
Providing a bright spot, China's services sector expanded in July at a healthy clip, in contrast to a struggling manufacturing sector, although surveys released on Friday showed some signs of weakness in new orders and pressure from overcapacity.
(Editing by Clarence Fernandez)