Secretary of State Mike Pompeo has gone on the offensive, defending President Donald Trump and suggesting that it was actually the Obama administration that was malfeasant in Ukraine.

In an interview with Fox News host Martha MacCallum on Wednesday night, Pompeo said that there was nothing wrong with Trump's July phone call to the Ukrainian president.

'What I know is I was on the call, I listened to the call, I thought the way the President handled it was appropriate,' he said.

The call is now at the center of a House impeachment probe, with Democrats alleging that Trump threatened to withhold military aid if Ukraine did not investigate his political rival Joe Biden.

In an interview with Fox News on Wednesday night, Pompeo said that there was nothing wrong with Trump's July phone call to the Ukrainian president

'This is the administration that provided defensive weapon systems to Ukraine,' Pompeo said of the Trump administration.

'The previous administration... I couldn't tell you why, I couldn't answer if it's because of Hunter Biden that Barack Obama and Vice President Biden didn't give defensive weapon systems to Ukraine,' he continued.

'They'll have to answer for that. Maybe I just don't have the full story,' Pompeo said.

At the heart of Ukraine President Volodymyr Zelensky's July 25 call with Trump was a request for the U.S. to sell that country Javelin anti-tank missiles.

After Zelensky suggested he wanted to buy more Javelins, Trump asked him for a 'favor' and then later urged him to investigate Hunter Biden.

The sale of the Javelins was approved by the State Department late last month.

The Obama administration did refuse to sell Ukraine lethal military hardware, as Pompeo asserted, under the stated justification that such sales would escalate tensions with Russia.

The Obama administration did refuse to sell Ukraine lethal military hardware - which Pompeo suggested had a connection with Joe Biden's son's dealings there

In other interviews, Pompeo repeated his assertion that former President Barack Obama and Vice President Biden may have corruptly withheld aid to Ukraine.

'This is the administration that actually provided defensive weapons systems [to Ukraine]. I could not tell you why the Obama administration chose not to [arm Ukraine]. Was it because of Hunter Biden? I don't know!' he told the New York Post on Wednesday.

Several commentators rejected Pompeo's premise, with New York Times diplomatic correspondent Edward Wong calling it a 'conspiracy theory.'

'This insinuation makes zero sense. Pompeo, the top US diplomat, doesn't seem to care anymore about trying to establish a reputation as a straight talker,' Wong wrote on Twitter.

NPR's diplomatic correspondent, Michele Kelemen, chimed in: 'The Obama admin did not give weapons to ukraine so as not to fuel the conflict. They made their case, like it or not.'

On Thursday, the House will vote on a resolution to formalize the Democrat's impeachment inquiry, which is expected to pass on partisan lines.

The resolution will give House Intelligence Committee Chairman new powers to oversee the process, and requires him to write a report with recommendations for the Judiciary Committee, which will draft and recommend articles of impeachment.