US West Texas Intermediate (WTI) crude CLc1 had gained 16 cents or 0.3 per cent to USD 52.97 a barrel.
Brent crude futures LCOc1 fell 30 cents, or 0.5 per cent, to USD 59.067 barrel.
Saudi Aramco officials as a matter of policy do not comment on the kingdom’s monthly OSPs.
The company has not given a specific timeline for the resumption of full output.
US crude was down 26 cents, or 0.5 per cent, at USD 54.84 a barrel by 0644 GMT, while Brent was down 6 cents at USD 58.60 a barrel.
WTI futures, slumped last week by nearly 2 million barrels to their lowest since December.
Tensions spiked between Iran and the West after Iranian commandos seized a British-flagged oil tanker in the Gulf.
Brent crude futures for September fell 21 cents to USD 66.51 a barrel.
Oil companies in the Gulf of Mexico had cut more than 1 million barrels per day (bpd) of output.
Oil prices are being pressured by ongoing worries about demand as the US-China trade war.