A trove of State Department documents obtained late Friday by watchdog group American Oversight provided new details on Secretary of State Mike Pompeo's involvement in the White House effort to pressure Ukraine to investigate President Donald Trump's political rivals.

The documents, which the State Department turned over in compliance with a Freedom of Information Act lawsuit, showed that Pompeo spoke to Trump's personal lawyer Rudy Giuliani by phone at least twice earlier this year as Giuliani was pressing Ukraine to probe former Vice President Joe Biden. At least one of the calls was arranged by Trump assistant Madeleine Westerhout, the documents showed.

Giuliani in March was also orchestrating a smear campaign against former U.S. Ambassador to Ukraine Marie Yovanovitch, who Trump removed from her post in May.

In April, following his calls with Giuliani, Pompeo also called Rep. Devin Nunes (R-Calif.), who has been implicated in the effort to dig up dirt on Biden.

We can see why Secretary Pompeo refused to release these documents to Congress: the paper trail connects him to Giuliani, showing a March 2019 call right before a call to Rep. Nunes. https://t.co/CjJflQYQqp pic.twitter.com/M3gVDHKymU — American Oversight (@weareoversight) November 23, 2019

Pompeo, who admitted last month that he was on the July 25 call between Trump and Ukrainian President Volodymyr Zelensky, has refused to cooperate with the House impeachment inquiry into Trump.

Austin Evers, executive director of American Oversight, said the newly released documents shed light on the reasons behind Pompeo's reluctance to testify or hand over information requested by impeachment investigators.

"We can see why Mike Pompeo has refused to release this information to Congress," Evers said in a statement. "It reveals a clear paper trail from Rudy Giuliani to the Oval Office to Secretary Pompeo to facilitate Giuliani's smear campaign against a U.S. ambassador."

"The evidence is only going to get worse for the administration as its stonewall strategy collapses in the face of court orders," added Evers. "That American Oversight could obtain these documents establishes that there is no legal basis for the administration to withhold them from Congress. That conclusively shows that the administration is engaged in obstruction of justice."

In an interview with the New York Times last month, Giuliani acknowledged that he spoke with Pompeo about Ukraine in late March.

As the Times reported late Saturday:

In connection with one such conversation, Mr. Giuliani said he provided Mr. Pompeo a timeline listing what he considered to be key events implicating targets of Mr. Trump, including the Bidens, Ms. Yovanovitch and Ukrainians whom Mr. Giuliani said had disseminated damaging information about Mr. Trump’s 2016 campaign chairman, Paul Manafort. Shortly after, Mr. Pompeo "called and said, 'Do you have any backup?'" Mr. Giuliani said in the interview. In response, Mr. Giuliani said, he had someone hand-deliver to Mr. Pompeo's office an envelope containing a series of memos detailing claims made by a pair of Ukrainian prosecutors in interviews conducted by Mr. Giuliani and his associates in January.

The State Department documents come just days after U.S. Ambassador to the European Union Gordon Sondland testified before the House Intelligence Committee that "everyone was in the loop" on Trump's effort to press Ukraine for an investigation into Biden.

In an interview on MSNBC Saturday, Rep. Ted Lieu (D-Calif.), a member of the House Judiciary Committee, said the American Oversight documents confirm Sondland's testimony.

"These documents show that Giuliani was not freelancing, that he was essentially talking to Secretary Pompeo," said Lieu. "Everybody was on the same page."