US crude oil prices have slipped back after strong gains as the White House prepared to announce a decision on whether it will withdraw from the Iran nuclear deal. US president Donald Trump wrote on Twitter on Monday that he would announce his decision on the Iran deal from the White House at 2pm on Tuesday. Mr Trump has repeatedly criticised the agreement between Iran and the US and its partners. If he opts to reimpose sanctions on Iran, it would probably entail reductions in the country’s oil exports and deliver a jolt to international markets.

West Texas Intermediate, the US oil benchmark, rose above $70 a barrel on Monday for the first time in more than three years but slipped back in Asia trading on Tuesday where it was trading down 1.2 percent at $69.87. Brent was off 1 percent at $75.45. WTI reached $70.84 on Monday, up 1.6 percent for the session and the highest level since November 2014, while North Sea’s Brent grade hit a three-and-a-half-year high of more than $76. Iran’s oil production has bounced back to nearly 4m barrels a day since world powers eased sanctions over its nuclear programme.

Reimposing sanctions could reduce Iranian oil exports by 200,000-300,000 barrels a day, according to RBC Capital Markets. Robust demand propelled by solid global economic growth, along with cuts in output co-ordinated by the Opec cartel, has diminished surplus oil stocks and left the market more sensitive to shocks. Concerns over supplies have also centred on Venezuela as economic turmoil dents its crude sales.  Venezuela’s oil production has fallen by nearly 600,000 b/d from a year ago due to “chronic mismanagement” inside the country, the International Energy Agency said.