December Brent crude futures , set to expire on Tuesday, rose 36 cents, or 0.41%, to stand at $87.81 a barrel by 0305 GMT.
"If this evolves into a full-scale invasion and there is involvement from Iran, tighter supply worries could resurface."
In a note, ING analysts said, "Disruptions to Iranian oil flows remain the most obvious risk to the market."
Such lost supply could range between 500,000 barrels per day (bpd) and 1 million bpd if the United States strictly enforces sanctions once again, they added, although Middle East developments had yet to affect oil supply.
Weaker-than-expected manufacturing and non-manufacturing activity data from China stoked fears of slowing fuel demand from the world's No.
Persons:
Eric Gaillard, Brent, Leon Li, China stoked, CME's, Laura Sanicola, Trixie Yap, Clarence Fernandez
Organizations:
REUTERS, . West Texas, Federal Reserve, Markets, ING, U.S, Thomson
Locations:
Nice, France, China, Wednesday's U.S, Gaza, Iran, Shanghai, Israel, United States, Venezuela, riven