WASHINGTON — Secretary of State Mike Pompeo said Saturday that he had sent a response to the House committees seeking documents in their impeachment inquiry of President Trump, but congressional investigators are still waiting for their subpoena to be complied with.

Also, Gordon Sondland, the U.S. ambassador to the European Union ensnared in the impeachment inquiry of Trump, has agreed to meet behind closed doors Tuesday with the three panels – Intelligence, Foreign Affairs and House Oversight – spearheading the probe, according to a committee aide. The official on Saturday confirmed the schedule on the condition of anonymity to discuss private deliberations. NBC News first reported Sondland’s planned appearance Saturday.

At a news conference with the foreign minister of Greece, Pompeo said he had sent a letter to Capitol Hill as “our initial response to the document request. We’ll obviously do all the things we’re required to do by law.”

His remarks came as Democratic-led House committees leading the impeachment investigation said that he failed to meet a Friday deadline to deliver subpoenaed State Department documents to them. “However, the State Department has contacted the committees on this matter, and we hope the Department will cooperate in full promptly,” a committee official said.

Pompeo repeated charges made a week ago that the congressional inquiries have “harassed and abused State Department employees” by contacting them directly and failing to go through proper channels to request both testimony and documents.

“I remember once, when I was on that side and we were looking for documents, I remember precisely how long it took for those documents to come across,” said Pompeo, a former House member from Kansas who, while in the majority, helped lead the Republican investigation of the Clinton-led State Departments actions in Benghazi, Libya regarding a 2012 terrorist attack that killed four American officials.

Pompeo, who has been on a weeklong trip to southern Europe, has been relatively closed-lipped about the impeachment inquiry unfolding in Washington, dismissing questions about it as political gamesmanship and a “silly gotcha game.” He is due to return to Washington on Sunday.

Regarding pressure on Ukraine to investigate activities there of Biden and his son, who served on the board of a major Ukrainian energy company, and Trump’s public invitation this week for China to help investigate Hunter Biden’s business activities there, Pompeo defended the president.

He also it was “very reasonable” and “our duty” to ask other governments to help investigate interference in the 2016 U.S. election, as Trump has. “There’s been some suggestion somehow that it would be inappropriate for the United States government to engage in that activity, and I see it as just precisely the opposite, Pompeo said. “I see our duty to engage in activity that ensures that we have fair, free elections.”

Asked later whether other countries, including Greece, could come under pressure based on their willingness to help the U.S. president, Pompeo laughed.

“It’s totally appropriate, right, isn’t that right? Yes, it’s totally right. . . . Nations do this, nations work together and they say ‘Boy, goodness gracious, if you can help me with “X” and we’ll help you achieve “Y”.’ This is what partnerships do. It’s win-win. It’s better for each of us.”

A whistleblower’s complaint revealed a July 25 call in which Trump pressed Ukraine’s Volodymyr Zelensky to investigate the activities of former vice president Joe Biden, a 2020 Democratic presidential candidate, and his son and subsequent efforts to restrict access to records of the call. It also alleged that Trump asked Zelensky to look into unproven allegations that Russia’s interference in the 2016 U.S. presidential election originated in Ukraine.

Trump again maligned the whistleblower, Democrats and the news media in tweets Saturday morning, baselessly calling The New York Times and The Washington Post “pure fiction.”

“The so-called Whistleblower’s account of my perfect phone call is “way off,” not even close. (Rep. Adam) Schiff and (Speaker Nancy) Pelosi never thought I would release the transcript of the call. Got them by surprise, they got caught. This is a fraud against the American people!” Trump also tweeted.

As part of their investigation, the committees subpoenaed the White House for documents on Friday, a step they had announced earlier in the week, and demanded documents from Vice President Mike Pence.

“During a press conference on Wednesday, President Trump was asked if he would cooperate with the House impeachment inquiry. He responded, ‘I always cooperate.’ President Trump’s claim is patently false,” the three committee chairmen wrote. “The White House has refused to engage with – or even respond to – multiple requests for documents from our Committees on a voluntary basis. After nearly a month of stonewalling, it appears clear that the President has chosen the path of defiance, obstruction, and cover-up.”

The three are Intelligence Committee Chairmen Adam Schiff, D-Calif., Foreign Affairs Eliot Engel, D-N.Y., and Oversight and Reform Elijah Cummings, D-Md.

Sondland, who will give his deposition next week, worked behind the scenes to carry out Trump’s wishes in a country that’s not part of the European Union. The ambassador met with Zelensky to give “advice” about how to “navigate” Trump’s demands, the whistleblower reported. And in text messages turned over to House investigators Thursday, Sondland insisted that Trump’s decision to withhold nearly $400 million in military aid to Ukraine was not a quid pro quo – as diplomat William “Bill” Taylor had feared, according to the texts.

“Bill, I believe you are incorrect about President Trump’s intentions,” Sondland wrote last month, before urging Taylor, the U.S. charges d’affaires in Ukraine, to call him instead.

Kurt Volker, the former U.S. envoy to Ukraine, spent some 10 hours behind closed doors on Thursday with the committees, providing a deposition and text messages.

Unlike Volker, who turned all his communications over to Congress, Sondland transmitted his texts and documents to the State Department, which means the committees will have to fight the agency for access to them.