Traders said they were also expecting news of new stimulus measures to boost the Chinese economy.
By early afternoon in Europe, benchmark oil for November delivery was up 94 cents to $90.92 a barrel in electronic trading in New York.
In London, Brent crude rose 97 cents to $111.01 a barrel on the ICE Futures exchange.
Analysts said harsh rhetoric over Iran's nuclear programme and threats by Israel of military action against Iranian nuclear installations renewed worries about oil supplies should an all-out conflagration erupt.
US President Barack Obama told the UN General Assembly earlier this week that he wants to resolve the dispute through diplomacy but that the time to do so is "not unlimited."
Obama also said the Iranian government has failed to demonstrate that its nuclear programme is peaceful.
