New York's main contract, light sweet crude for delivery in October, climbed 47 cents to 70.18 dollars per barrel in electronic deals before the official opening of the US market.

In London, Brent North Sea crude for October delivery gained also 47 cents to 70.33 dollars per barrel in electronic deals.

Oil prices had Tuesday fallen below 70 dollars in New York and London on reduced fears that tropical storm Ernesto would damage US Gulf coast oil facilities, traders said.

All eyes Wednesday were on Iran, the world's fourth biggest producer of crude oil.

The United Nations nuclear watchdog was expected Thursday to confirm that Iran has failed to suspend strategic nuclear fuel work, opening the door to possible UN sanctions against Tehran.

Analysts say that Iran could disrupt its oil exports if hit by sanctions, a move that could send oil prices soaring.