He was referring to a conspiracy theory that a hacked Democratic National Committee computer server was taken to Ukraine in 2016 to hide evidence that Kiev, not Moscow, interfered in the last US presidential election.

Mulvaney also said the military funds had been withheld because European countries were being “really, really stingy when it comes to lethal aid” for Ukraine.

But he characterised the decision to leverage congressionally approved aid as common practice, citing other instances in which the Trump administration has withheld aid to foreign countries and telling critics to “get over it”.

“I have news for everybody: get over it. There’s going to be political influence in foreign policy,” Mulvaney said. “Elections do have consequences and they should, and your foreign policy is going to change … there’s no problem with that.”

The acting chief of staff later walked back his remarks on Trump withholding military aid to Ukraine as a quid pro quo to get the country to investigate Democrats. 

“Let me be clear, there was absolutely no quid pro quo between Ukrainian military aid and any investigation into the 2016 election,” Mulvaney said in a statement on Thursday evening.

“The president never told me to withhold any money until the Ukrainians did anything related to the server. The only reasons we were holding the money was because of concern about lack of support from other nations and concerns over corruption.“

Earlier on Thursday, Mulvaney also reacted to comments from US ambassador to the European Union Gordon Sondland, who met House impeachment investigators behind closed doors. Sonland said that Trump outsourced the job of handling US policy on Ukraine to Trump’s personal lawyer Rudy Giuliani, a decision that made Sondland uncomfortable but one he still carried out.

“I would not have recommended that Mr Giuliani or any private citizen be involved in these foreign policy matters,” Sondland said, according to his prepared remarks obtained by The Washington Post.

Trump called her ‘bad news’. Now ex-Ukraine envoy is defying him to testify

Mulvaney shot down those concerns, defending the president’s right to put foreign policy in the hands of his personal lawyer.

“You may not like the fact that Giuliani was involved, that’s great, that’s fine,” Mulvaney said, referencing Sondland’s remarks. “It’s not illegal, it’s not impeachable … the president gets to set foreign policy and he gets to choose who to do so, as long as it doesn’t violate any law.”

Sondland, a major Trump donor who has become a focus of the impeachment inquiry because of his outsize role in US-Ukraine policy, criticised the president’s temporary hold on aid and the recall of the former US ambassador to Ukraine, Marie Yovanovitch.

Sondland called her an “excellent diplomat” and said he “regretted” her departure, which followed a campaign by Giuliani to paint her as disloyal to the president.

Sondland is expected to face an onslaught of questions from Democrats, who have accused the president of abusing his power to pressure Ukraine to help his 2020 re-election campaign.

Trump has denied any wrongdoing, and has said his decision to withhold military aid was out of frustration that European governments were not doing more to assist the country.

In his remarks, Sondland said in principle he opposes any “quid pro quo” that would exchange US support to a friendly nation for an investigation into Trump’s political rival, former vice-president Joe Biden.

Trump defends his ‘legendary’ lawyer Giuliani … for now 

But he said he became aware only recently that Trump’s efforts to investigate an obscure Ukrainian energy company named Burisma were due to its associations with Biden, whose son Hunter worked for the energy company. Joe Biden is a leading Democratic candidate for president.

“I did not understand, until much later, that Mr Giuliani’s agenda might have also included an effort to prompt the Ukrainians to investigate Vice-President Biden or his son or to involve Ukrainians, directly or indirectly, in the president’s 2020 re-election campaign,” he said.

“Although Mr Giuliani did mention the name ‘Burisma’ in August 2019, I understood that Burisma was one of many examples of Ukrainian companies run by oligarchs and lacking the type of corporate governance structures found in Western companies.”

Sondland’s ostensible failure to connect the dots between Burisma and the Bidens occurred as Giuliani made several televised appearances over the spring and summer criticising Hunter Biden’s involvement on the board, and numerous newspaper and magazine articles questioned whether his role at Burisma could prove to be a drag on his father’s presidential campaign.

In his testimony, Sondland, a hotel magnate who came to the job with no diplomatic experience, depicts himself as a well-meaning but in some cases out of the loop emissary for the president who tried to do what he could to prop up the government of Ukraine as it fends off Russian-backed separatists.

“My goal has always been to advance US interests in securing a strong relationship with Ukraine,” he said in his remarks.

“Withholding foreign aid in order to pressure a foreign government to take such steps would be wrong. I did not and would not ever participate in such undertakings.”

Parts of his testimony appear to conflict with the testimony of other officials this week, including Fiona Hill, the National Security Council’s former senior director for Russia and Europe.

Hill told House investigators that she was concerned by Sondland’s talk of investigations in a July meeting, which she eventually relayed to a lawyer for the National Security Council.

Sondland, in his opening remarks, said he was never aware of objections from her or her boss, national security adviser John Bolton.

“I have to view her testimony – if the media reports are accurate – as the product of hindsight and in the context of the widely known tensions between the NSC, on the one hand, and the State Department, on the other hand,” he said.

Sondland claims that his pursuit of investigations in Ukraine were always in line with long-standing US policy to push for transparency and anti-corruption efforts in the country.

Additional reporting by Bloomberg