A U.S. attack on Iranian nuclear sites could lead to a knee-jerk reaction in global markets when they reopen, sending oil prices higher and triggering a rush to safety, investors said, as they assessed how the latest escalation of tensions would ripple through the global economy.

Traders say crude could rise beyond $US100 a barrel, making it harder for the RBA to continue cutting interest rates as anticipated this year.

Following the United States of America strike, which hit Iran's three nuclear sites—Natanz, Isfahan, and Fordo, on Saturday, the global oil prices are