Steven Mnuchin was sworn in Monday as U.S. Treasury Secretary following a 53-47 Senate vote divided along party lines.

During the ceremony at the White House, President Donald Trump called Mnuchin "a financial legend with an incredible track record of success” who would now work for the American taxpayer.

"He'll work 24 hours a day, I know him. He'll work 28 hours a day if they give him the extra four hours," Trump said.

Mnuchin is expected to help Trump deliver on his pledge for a major tax reform, as well as play a key role in sanctions against foreign states, groups and individuals.

Hours before the new secretary was sworn in, the U.S. Treasury sanctioned Tareck El Aissami, who became Venezuela's Vice President last month, for being a leading actor -- "kingpin" -- in international narcotics trade, freezing his assets in the U.S. and barring Americans from doing business with him.

At the Senate vote for Mnuchin's confirmation earlier in the day, Republican Senator Orrin Hatch of Utah, who heads the Senate’s finance committee, hailed the businessman's experience “managing large and complicated private-sector enterprises and in negotiating difficult compromises and making tough decisions -- and being accountable for those decisions”.

According to Senate Majority Leader Mitch McConnell from Kentucky, Mnuchin "is smart, he's capable, and he's got impressive private-sector experience”.

However, Democrats decried Mnuchin’s business strategies while in private sector. Senator Debbie Stabenow of Michigan said: “Mr. Mnuchin has made his career profiting from the misfortunes of working people.”

Stabenow referenced the 2008 collapse of the IndyMac bank and Mnuchin’s initiative to buy the bank a year later with a group of investors, rename it OneWest and turn it around, before selling it for profit in 2014.

The bank under Mnuchin’s ownership was “notorious for taking an especially aggressive role in foreclosing on struggling homeowners,” Stabenow said.

Senator Sheldon Whitehouse of Rhode Island said: "I simply cannot forgive somebody who took a look at that banking crisis and took a look at the pain that Wall Street had sent in a wave across all of America, and thought, 'Ah, there's a great new way to make money, foreclosing on people.'"

Mnuchin, 54, defended himself by saying he worked hard to offer refinancing to homeowners to allow them to keep their homes, adding that his bank provided borrowers with more than 100,000 loan modifications.

In a less divisive vote late Monday, the Senate unanimously backed the appointment of David Shulkin to helm the Department of Veteran Affairs.

The 57-year-old physician, who served as the department’s top health official, won the backing of Democrats for his pledge to prioritize veterans’ issues over party politics. He has ruled out privatizing the department or ordering mass staff replacements.