Treasury Secretary Steven Mnuchin on Monday made Iran oil sanctions a top part of a meeting with Saudi Crown Prince Mohammed bin Salman that took place amid heightened tensions between the U.S. and Saudi Arabia over the murder of journalist Jamal Khashoggi.

Mnuchin also reiterated the Trump administration's support for the kingdom's Vision 2030 plan to diversify the economy away from oil, according to a readout of the meeting.

U.S. sanctions on Iran's oil exports kick in on Nov. 4, and the Trump administration is relying on Saudi Arabia's oil production to make up for any shortfalls in supply in order to curtail a surge in fuel prices.

Mnuchin told Reuters on Sunday that if countries want waivers from the U.S. they will have to agree to reduce their consumption of Iranian crude oil by a higher amount in the future. “I would expect that if we do give waivers it will be significantly larger reductions,” Mnuchin told a news agency in Israel as part of his Mideast trip.

Mnuchin will not be attending an investment conference on Tuesday in the Saudi capital focused on the 2030 plan. The secretary canceled his attendance in response to the investigation into slain Saudi journalist and U.S. permanent resident Jamal Khashoggi.

"To make clear @stevenmnuchin1 cancelled his speaking engagement at Saudi investment conference. He is in Saudi (as part of 6 country Middle East trip) visiting the Terrorist Financing Targeting Center and having meetings in preparation for Iran sanctions," Tony Sayegh, Mnuchin's spokesman, tweeted.

"In his meeting with the Saudi Crown Prince, @stevenmnuchin1 addressed combating terrorist financing, implementing Iran sanctions, Saudi economic issues and the Khashoggi investigation," Sayegh said in a separate tweet.

The two "stressed the importance of the Saudi-US strategic partnership and the future role of this partnership in accordance with the Kingdom's Vision 2030," the government's Saudi Press Agency said in its readout of the meeting.

"The bilateral relations between the Kingdom of Saudi Arabia and the United States of America were also reviewed on both the trade and investment sides and the opportunities for their development," the agency reported. "The meeting touched on a number of issues, including joint efforts in the fight against corruption and the financing of terrorism."