Brent sweet crude for new July delivery was up 1 cent at 74.70 dollars.
U.S. West Texas Intermediate crude for June delivery was up 2 cents at 68.59 dollars a barrel by 0649 GMT,
Oil prices rose on Monday after Israeli Prime Minister Benjamin Netanyahu stepped up pressure on the U.S. to pull out of the 2015 nuclear-deal with Iran, presenting what he called evidence of a secret Iranian nuclear weapons programme.
Tehran has denied ever seeking nuclear weapons.
Trade was quiet in Asia as many markets, including China, India and Singapore were closed for public holidays.
Trump has given Britain, France and Germany a May 12 deadline to fix what he views as the deal’s flaws or he will reimpose sanctions.
“There are worries that Iran’s oil exports could fall by about 1 million barrels per day from current levels,” said Tomomichi Akuta, senior economist at Mitsubishi UFJ Research and Consulting in Tokyo.
“If that happened, Brent prices could jump to near 90 dollars (a barrel).” (Reuters/NAN)