New York's main contract, light sweet crude for delivery in August, fell 18 cents to 73.91 dollars per barrel in electronic deals before the official re-opening of the US market.

The contract had hit a historic 75.78 dollars last Friday owing to simmering geopolitical tensions, particularly over Iran and North Korea.

Brent North Sea crude for August delivery lost 12 cents to 73.13 dollars per barrel in electronic trading on Monday. It had touched a record 75.09 dollars on Friday.

"The market is probably still anxious about developments in North Korea and the Middle East," said Mark Pervan, an analyst with Melbourne-based Daiwa Securities.

"Oil premiums won't be washed out in the short-term."

The dispute between Iran -- the world's fourth-largest crude producer -- and Western powers over its nuclear programme is a key geo-political factor concerning the market, dealers said.

Iran had said on Sunday that it would take until the second half of August to respond to an international offer of incentives in return for the suspension of sensitive nuclear work.

The United States has meanwhile threatened UN action against the Islamic republic if it fails to heed international concerns.