* Sanctions against Iran oil exports to start Nov. 4
* U.S. rig count at highest since 2015: https://tmsnrt.rs/2PfF6i3
* ICE to launch new U.S. crude export futures contract
* Other producers will struggle to replace Iran shortfall - IEA
* But U.S.-China trade war clouds 2019 outlook (Adds quote on trade dispute, launch of new ICE crude contract)
SINGAPORE, Oct 22 (Reuters) - Oil prices edged up on Monday, as markets were expected to tighten once U.S. sanctions against Iran's crude exports are implemented next month.
Front-month Brent crude oil futures were trading at $79.88 a barrel at 0248 GMT, 10 cents above their last close.
U.S. West Texas Intermediate (WTI) crude futures were at $69.31 a barrel, 19 cents above their last settlement.
Also in the United States, Intercontinental Exchange said its new Permian West Texas Intermediate crude futures contract deliverable in Houston, Texas, will begin trading on Monday.
The main price driver in Asia on Monday was the looming start of U.S. sanctions against Iran's oil exports, which will start on November 4.
While the Organization of the Petroleum Exporting Countries (OPEC) agreed in June to boost supply to make up for expected Iran disruptions, an internal document reviewed by Reuters suggested that OPEC is struggling to add barrels to the market as an increase in Saudi Arabian supply was offset by declines in Iran, Venezuela and Angola.
Fatih Birol, executive director of the International Energy Agency (IEA), said on Monday that other producers may struggle to fully make up for the expected fall in Iranian supply, and that coupled with strong demand, oil prices could rise further.
Traders said major oil consumers were stockpiling in anticipation of more disruptions.
"In China, higher seasonal demand and suspected stockpiling are occurring, while similarly the U.S. and the OECD continue building stockpiles ahead of potential supply disruptions this winter," said Stephen Innes, head of trading for Asia/Pacific at futures brokerage Oanda in Singapore.
Despite this, Innes said overall global oil supply was currently enough to meet demand.
There were also some signs of rising output, especially in North America.
U.S. drillers added four oil rigs in the week to Oct. 19, bringing the total count to 873, Baker Hughes energy services firm said on Friday, raising the rig count to the highest level since March 2015. <RIG-OL-USA-BHI>
The U.S. rig count is an early indicator of future output. With activity rising again after months of stagnation, U.S. crude production is also expected to continue to rise.
Looking further out, concern that the trade dispute between the United States and China would crimp economic growth may weigh on the outlook for oil prices.
"The full impact of the U.S.-China trade war will hit markets in 2019 and could act as a considerable drag on oil demand next year, raising the possibility of the market returning to surplus," said Emirates NBD bank in a note.
Shipping brokerage Eastport said on Monday that "Chinese manufacturing is beginning to slow" and that "Trump's proposal of slapping...tariffs on additional...Chinese goods from 1 January would be a further drag on trade."
(Reporting by Henning Gloystein Editing by Richard Pullin and Kenneth Maxwell)