Democratic Rep. Adam Schiff on Tuesday said the State Department is withholding messages from Gordon Sondland, the ambassador to the European Union, whom the Trump administration directed not to appear for a House impeachment deposition.

“Not only is the Congress being deprived of his testimony … but we are also aware that the ambassador has text messages or emails on a personal device, which had been provided to the State Department,” the House Intelligence Committee chairman told reporters.

He said that the committee requested the messages from the ambassador, but that “the State Department is withholding those messages as well.”

Schiff added: “Those messages are also deeply relevant to this investigation and the impeachment inquiry. The failure to produce this witness, the failure to produce these documents we consider yet additional strong evidence of obstruction of the constitutional functions of Congress.”

He said Sondland “was a key player in efforts to obtain a commitment from Ukraine to investigate a bogus conspiracy theory about the 2016 election, as well as Joe Biden and his son.

“And we know that the ambassador has relevant evidence on whether the meeting with the president that the Ukrainians desperately sought with President Trump was being conditioned on these investigations that the president believed would help his re-election campaign.

“It’s hard to [overstate] the significance of not just Ambassador Sondland’s testimony and the documents, but the testimony of others as well,” he said.

Rep. Jim Jordan, the ranking member of the House Oversight Committee, said later that Republicans understand why the State Department blocked Sondland’s testimony.

“It’s based on the unfair and partisan process that Mr. Schiff has been running,” Jordan said.

“You think about what the Democrats are trying to do: impeach the president of the United States 13 months prior to an election, based on an anonymous whistleblower with no firsthand knowledge who has a bias against the president,” he added.