Wisconsin senator Ron Johnson, chairman of the Senate homeland security committee, cited the president's claim that he had withheld almost $400 million in military assistance because he was concerned that the EU was not doing enough.
Mr Trump has given various reasons for withholding the aid, including that he was concerned about corruption in the former Soviet state.
However, figures suggest that Europe has been giving more financial support to Ukraine in its battle against Russian-backed separatists than the United States.
Appearing on CNN's State of the Union, Mr Johnson said the president had held up aid because of concerns about corruption in Ukraine.
He said Mr Trump had asked him: "Why isn't Europe stepping up to the plate? I talk to Angela Merkel and say, why don't you provide funding for these things and Angela Merkel tells me, because you will -- hey Ron, we're shmucks."
At that point Tapper interrupted to say: "It's not true that Europe doesn't help the Ukraine -- this is not you saying it, it's President Trump. I just want our viewers to know. I want to correct the one thing that President Trump said,
"Because the Organisation of Economic Cooperation and Development says that the EU contributed $425.2 million on average for 2016/2017. The US was second with $204 million.
"Again, I'm not fact-checking you -- the president's impression is incorrect."
The senator is no stranger to being given a hard time on Sunday morning political shows.
Last month he was involved in a furious exchange with Chuck Todd, host of NBC's Meet the Press, after he was accused of peddling baseless conspiracy theories in an apparent attempt to distract from the president's mounting difficulties.
This weekend another Republican -- congressman Mac Thornberry -- came up with a novel defence of the president, saying that while it was inappropriate for him to have asked a foreign country to help discredit a political opponent, he should not be impeached for it because it's the way he acts "all the time".
Mr Thornberry told ABC's This Week: "There's not really anything the president said in that phone call that's different to what he says in public all the time.
"So is there some sort of abuse of power that rises to that threshold that is different than the American people have been hearing for three years? I don't hear that."