New York's main contract, light sweet crude for delivery in September, gained 23 cents to USD 92.96 a barrel, while Brent North Sea crude for September advanced two cents to USD 113.62.
Crude prices were up "on concerns about North Sea supply and Middle East tensions," Phillip Futures said in a report.
North Sea crude supply is set to be curtailed in September primarily by the shutdown of an oil field for scheduled maintenance.
And speculation was mounting in the Israeli press about a possible strike on Iran, with the newspaper Haaretz reporting top officials believe the time is fast approaching for a decision by the government.
The US yesterday insisted that there is still time for a diplomatic way out of the West's nuclear showdown with Iran, which denies claims it is trying to build a nuclear bomb.
The White House said there remains a "window" for its strategy of pressure through punishing sanctions, adding that world power talks with Tehran could work despite the absence of a breakthrough so far.