By Henning Gloystein
International benchmark Brent crude oil futures were at $85.04 per barrel at 0606 GMT, up 6 cents from their last close, and not far off the $85.45 peak reached in the previous session, the highest since November 2014.
Brent has risen by around 20 percent from its most recent lows in August.
U.S. West Texas Intermediate (WTI) crude futures were up 28 cents, or 0.4 percent, at $75.58 a barrel.
WTI is up about 17 percent since mid-August.
Sentiment was lifted by a last-gasp deal to salvage NAFTA as a trilateral pact between the United States, Mexico and Canada, rescuing a $1.2 trillion a year open-trade zone that had been about to collapse.
More fundamentally, oil markets have been pushed up by looming U.S. sanctions against Iran's oil industry, which at its most recent peak this year supplied almost 3 percent of the world's almost 100 million barrels of daily consumption.
Trade data in Refinitiv Eikon showed Iran's seaborne exports in September were just 1.6 million barrels per day, the lowest level since mid-2016.
"Oil prices continue to climb, supported by the nearing Iran embargo and related supply concerns," said Norbert Ruecker, head of commodity research at Swiss bank Julius Baer.
"The supply situation looks fragile indeed, as any additional shortfall such as a deterioration of the situation in Venezuela would tighten oil supplies."
HSBC said in its fourth quarter Global Economics outlook that "our oil analysts believe there is now a growing risk it (crude) could touch $100 per barrel".
Washington's sanctions are set to start on Nov. 4, and analysts say there may not be enough spare production capacity in the short-term to meet demand, potentially requiring large storage drawdowns.
"The camp of believers that $100 oil could be reached continues to expand, with spare capacity concerns continuing to grow," said Brian Kessens, managing director at investment services firm Tortoise.
The Organization of the Petroleum Exporting Countries (OPEC), of which Iran is a member, has struggled to replace export falls from Iran, according to a Reuters survey published on Monday.
With crude prices soaring and many currencies in emerging markets, including India's rupee and Indonesia's rupiah declining, analysts warn that economic growth may be eroded.
"Admittedly, supply-side concerns are pushing the oil price higher, but there are now clear warning signs on the demand-side, which could yet send prices lower," said Capital Economics in a note to clients.
(Reporting by Henning Gloystein; Editing by Joseph Radford and Richard Pullin)
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)