Former Treasury Secretary Mnuchin says Trump's top priorities will be tax cuts, Iran sanctions and tariffs

President-elect Donald Trump likely will return to cornerstones of his previous economic platform such as tariffs, lower taxes and sanctions when he assumes office in January, his former Treasury secretary said Thursday.

Steven Mnuchin, who held the post throughout Trump's first term from 2017-21, told CNBC that he sees those items as critical to the Republican's agenda.

Tax cuts are "a signature part of his program," Mnuchin said in a "Squawk Box" interview. "I think that should be easy to pass in Congress, particularly if the Republicans control the House as well, which it looks like it will be."

Also on the agenda would be tariffs, which Trump implemented on multiple items during his first term and promised to do again.

"I think that tariffs do need to be used to get counterparties back to the table, especially China, which is not living up to all of the agreements they made," Mnuchin said.

Finally, he indicated that nations such as Iran and Russia can expect to see sanctions again. The Trump administration levied measures against petroleum producers in Iran in 2019 because they were owned by the Revolutionary Guard.

"The sanctions on Iran and Russia were very impactful. In the case of Iran, they're now selling millions of barrels of oil, which needs to be stopped," Mnuchin said.

Outside of those issues, Mnuchin, who said he likely would not take an official role in the Trump administration but would "be happy to serve from the outside," expects Trump to take on other issues such as steep deficit spending.

"I think he's in a position now, particularly with this overwhelming result, to take on difficult issues, and I think that's got to be part of government spending," he said.

Mnuchin is the founder of Liberty Strategic Capital.