Trump officials this weekend defended Trump from attacks over phonecalls in which he discussed calls for an investigation into Joe Biden's son over business activities in Ukraine.

Steve Mnuchin told CNN's Jake Tapper on Sunday it was wrong Biden's son worked in Ukraine while his father served in Barack Obama's administration.

When presented with the fact that Trump's children have foreign business interests while he sits in the Oval Office Mnuchin said he didn't want to "go into more of these details."

Tapper then accused the US treasury secretary of "setting a precedent that the president is violating."

Secretary of State Mike Pompeo, and Senator Lindsay Graham also stood behind Trump on network TV Sunday and called for a new investigation into Biden.

Biden was accused of pressuring Ukraine to fire a prosecutor investigating his son's employer in 2016. Ukrainian officials said in May 2019 there was no evidence the Bidens committed any wrongdoing.

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Donald Trump allies are scrambling to justify reports he pressured Ukraine to investigate Hunter Biden, but are seemingly struggling to see the irony of his children doing business around the world.

On Sunday, US Treasury Secretary Steven Mnuchin was grilled by CNN's Jake Tapper over a call where Trump reportedly asked Ukranian President Volodymyr Zelensky to look into Hunter Biden eight times.

Earlier that day Trump had confirmed he discussed Biden and his son during the July 25 call.

Appearing on CNN's "State of the Union" Mnuchin suggested it was wrong that Biden's son did business around the world while his father was Barack Obama's vice president.

Steve Mnuchin appearing on CNN's "State of the Union" to defend Donald Trump on Sunday. CNN

But Mnuchin failed to provide a clear answer when Tapper flipped the scenario to note that Trump's children work abroad while he is in office, and that Mnuchin was "setting a precedent that the president is violating."

Here's the full exchange between Mnuchin and Tapper.

TAPPER: If for instance, President Obama had pressured a foreign leader, Putin or the president of Ukraine, anyone said "I want you to look into Donald Trump Jr., or I want you to look into Eric Trump," international businessmen, both of them, would you not find that inappropriate? MNUCHIN: Again I'm not going to speculate on that. What I do find inappropriate is the fact that Vice President Biden at the time's son did very significant business dealings in Ukraine. I, for one, find that to be concerning and to me that is the issue perhaps that should be further investigated. TAPPER: Well I don't understand, so it's okay for Donald Trump Jr. and Eric Trump to do business all over the world, it's okay for Ivanka Trump to have copyrights approved all over the world while President Trump is president and while vice president Joe Biden his son shouldn't be able to do business dealings. MNUCHIN: Again I don't really want to go into more of these details other than to say... TAPPER: ...Well, you're setting a precedent that the president is violating. MNUCHIN: Again, I think there is a significant difference in what you're saying, okay. What I was saying between Biden and his son's relationship with the Ukraine oligarch and potential business dealings that the Trump Organization has had which predated his presidency.

Donald Trump (L) and Joe and Hunter Biden (R.) Associated Press/Evan Vucci, AP

Also on Sunday, Lindsey Graham, the chairman of the Senate's judiciary committee told Fox News that now is the time for the Department of Justice to investigate Hunter Biden's dealings in Ukraine, and what his father knew of them.

"What I'm asking for is for us to take some time and effort to look at what the Ukraine may have done in the 2016 election," he said on "Sunday Morning Futures With Maria Bartiromo."

"What role, if any, did the Bidens have to the Ukraine? Was it proper? Was it not?"

Read more: A mysterious exchange between Trump and a foreign leader is Washington's latest obsession. Here's what is actually going on.

Appearing on ABC's "The Week" Secretary of State Mike Pompeo said if Biden was protecting his son's business interests in Ukraine then US needs "to get to the bottom of that."

U.S. Secretary of State Mike Pompeo said that the US needs to "get to the bottom" of reports Joe Biden protected his son's business interests in Ukraine. Reuters

Biden was accused in 2016 of asking Ukraine to fire prosecutor general Viktor Shokin while he was investigating Burisma Group. Hunter Biden held a position on Burisma's board at the time.

Read more: Biden demanded Trump release transcripts of a call where he reportedly badgered Ukraine's leader to investigate his son 8 times

Ukraine's prosecutor general told Bloomberg in May 2019 he'd found no evidence that Joe or Hunter Biden had committed any wrongdoing.

2012 presidential nominee Mitt Romney broke rank from his Republican Party colleagues on Sunday to say it would be "troubling in the extreme" if allegations that Trump asked Zelensky to probe Hunter Biden were true.