Global oil prices have hit their highest level since May on fears of a resumption of fighting between the US and Iran in the Middle East.

At one point during trading on Friday the global benchmark Brent crude was up 4% at just over $US113 ($NZ198) a barrel.

West Texas Intermediate, which was more closely linked to the US market, was up 3% to just under $US100 a barrel.

The spike follows reports in The New York Times that the Trump Administration has drawn up plans for renewed strikes on Iran after next month's US midterm election.

In addition, the US has reportedly ordered some non-emergency government staff to leave Saudi Arabia.

That comes as Iran-backed Houthi rebels continue to target Saudi Arabia with missile strikes.

Global oil prices peaked this year at $US126 a barrel in April, in the wake of the US-Iran war.

Petrol prices in New Zealand tend to lag global oil price moves by a week or two.

According to fuel monitoring website Gaspy, the average price of 91 unleaded is around $3.55 per litre, down slightly on where it was earlier this month.

Diesel is $3.18 per litre.