Vice President Mike Pence said on CBS' "Face the Nation" on Sunday that there was no quid pro quo involved in President Trump's desire for Ukraine to open political investigations, despite testimonies from top State Department officials that suggest otherwise.

The exchange:

MARGARET BRENNAN: "We have had at least four U.S. officials under oath say that they had knowledge of a deal being offered that made military aid and a meeting with the president contingent on opening an investigation that relates to the company Joe Biden's son served on the board of. Are they all lying?"

PENCE: "I can only tell you what I know. And what I know is that the transcript of the president's call with President Zelensky shows that there was no quid pro quo. He did nothing wrong. In all of my interactions with President Zelensky, we focused entirely on President Zelensky's agenda to bring about reforms to end corruption in Ukraine and to bring together the European community to provide greater support for Ukraine. President Zelensky said there was no pressure."

Why it matters: Bill Taylor, the top U.S. diplomat in Ukraine, testified to House investigators this month that nearly $400 million of congressionally approved military aid was contingent on Ukraine opening investigations into allegations of interference in the 2016 election and the natural gas company Burisma, where Hunter Biden sat on the board. U.S. Ambassador to the EU Gordon Sondland testified that there was a quid pro quo involving the investigations and a White House visit for Zelensky.

Pence argued that the summary of Trump's July phone call with Ukraine's president does not show any quid pro quo, but the testimonies collected in the House impeachment investigation thus far go beyond the phone call.

Several officials have alleged there was a months-long pressure campaign led by Rudy Giuliani — in effect, a shadow foreign policy run outside of traditional administration channels.

Go deeper: Ukraine felt early Trump pressure and knew of military aid freeze