* Brent at Nov. 2014 high: tmsnrt.rs/2xATyY1
* U.S. sanctions to target Iran's oil exports from Nov. 4
* OPEC, Russia so far resist calls to raise output
* High oil prices threaten emerging market growth (Updates prices, chart)
By Henning Gloystein
SINGAPORE, Sept 25 (Reuters) - Brent crude oil prices hit a fresh four-year high on Tuesday amid looming U.S. sanctions against Iran and an apparent reluctance by OPEC and Russia to raise output to offset the expected to hit to supply.
Brent crude futures rose to $81.69 a barrel shortly after 0600 GMT, a level not seen since November 2014. They were still at $81.50 at 0655 GMT, up 30 cents, or 0.4 percent from their last close.
U.S. West Texas Intermediate (WTI) crude futures were at $72.28 a barrel, up 20 cents, or 0.3 percent from their last settlement.
The United States from Nov. 4 will target Iran's oil exports with sanctions, and Washington is putting pressure on governments and companies around the world to fall in line and cut purchases from Tehran.
"Iran will lose sizeable export volumes, and given OPEC+ reluctance to raise output, the market is ill-equipped to fill the supply gap," Harry Tchilinguirian, global head of commodity markets strategy at French bank BNP Paribas, told the Reuters Global Oil Forum on Tuesday.
OPEC+ groups members of the Organization of the Petroleum Exporting Countries (OPEC) and non-OPEC supplier Russia, who together agreed to curtail output starting in 2017.
While Britain, China, France, Germany, Russia and Iran on Monday said they were determined to develop payment mechanisms to continue trading despite the sanctions by the United States, most analysts expect Washington's actions to knock between 1 million and 1.5 million barrels per day (bpd) of crude oil supplies out of markets.
U.S. President Donald Trump has demanded that OPEC and Russia increase their supplies to make up for the expected fall in Iranian exports. Iran is the third-largest producer in OPEC.
OPEC and Russia, however, have so far rebuffed such calls.
"Any formal decision on oil output by the producer group, barring an extraordinary meeting, will only take place at the December meeting. Thus the window period for oil prices to potentially extend gains is quite wide as Iran loses exports and OPEC+ remains on standby," Tchilinguirian said.
Ashley Kelty, oil analyst at financial services firm Cantor Fitzgerald said crude could soon hit $90 per barrel.
"We don't believe OPEC can actually raise output significantly in the near term, as the physical spare capacity in the system is not that high," Kelty said.
"If OPEC is physically unable to ramp up production, then oil prices do indeed have much further to run," said Stephen Innes, head of trading for Asia-Pacific at futures brokerage OANDA in Singapore.
Bank of America Merrill Lynch lifted its average Brent price forecast for 2019 from $75 per barrel to $80, and increased its WTI forecast by $2 to $71 per barrel.
It said "the Iran factor may dominate the market near-term and cause a (crude price) spike," although it added that emerging market "demand concerns could reappear thereafter."
Indian refiners, hit by high crude prices and a sliding rupee, are planning to reduce oil imports in what could be a sign that high prices are starting to hurt demand.
Despite the bullish sentiment, commodity merchant Vitol said current prices already reflected the tighter market, and that more oil would be coming in 2019.
Vitol also said that non-OPEC producers, especially the United States, may insert up to 2 million bpd of new crude into the market in 2019.
To reflect rising U.S. oil exports, CME Group Inc said on Monday it will launch a WTI Houston crude futures contract in the fourth quarter.
CME's announcement comes after rival Intercontinental Exchange said in July it would offer a Houston crude futures contract.
Reporting by Henning Gloystein; Editing by Tom Hogue and Richard Pullin