WASHINGTON (AP) — Exactly what is Gordon Sondland's story? Certainly it's full of international mystery, which House impeachment investigators are sorting through as they probe President Donald Trump's pressure on Ukraine to investigate Joe Biden. But the intrigue is largely due to other witnesses recalling conversations with Sondland that he did not mention to impeachment investigators.

Trump's ambassador to the European Union, an Oregon hotelier and million-dollar Trump donor, Sondland has said he cannot recall many of the episodes involving him that others have recounted in colorful detail. What he does recall he sometimes remembers differently.

The discrepancies with other witnesses, and Sondland's with himself, matter as he testifies Wednesday under oath and penalty of perjury.

With the hearings underway Wednesday, here's what to watch:

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AT ISSUE

Listen for how Sondland describes his role in Trump's Ukraine policy and whether that policy was to hold up military aid until Ukraine made a public announcement that it was investigating Biden's son Hunter Biden.

Former White House national security aide Fiona Hill testified in private that Sondland informed her that he was in charge of Ukraine policy because the Republican president said so.

Asked about that conversation during a deposition, Sondland said: "I don't recall. I may have; I may not have. Again, I don't recall."

Besides, he says now that he viewed his role on Ukraine as one of support rather than leadership.

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JULY 10 MEETINGS

Testimony from multiple witnesses have described a pair of pivotal, sometimes tense, meetings at the White House on July 10 involving combinations of U.S. and Ukrainian leaders. Several of those present say Sondland explicitly connected a coveted White House visit to a public announcement by Ukraine of corruption investigations.

Army Lt. Col. Alexander Vindman remembers Sondland saying that day that the Ukrainians would have to deliver an investigation into the Bidens.

Sondland tells a different version, saying he doesn't recall mentioning Ukraine investigations or Burisma, the gas company on whose board Hunter Biden served. The only conflict he describes from that day is a disagreement on whether to promptly schedule a call between Trump and Ukrainian President Volodymyr Zelenskiy. Sondland was in favor.

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EVERYTHING'

William Taylor, the acting U.S. ambassador in Ukraine, told lawmakers that Sondland said that "everything" Ukraine wanted — a White House visit for its new leader and the release of military aid — was contingent on a public announcement of investigations into the 2016 election and into Burisma.

Sondland tells a more complex story.

In his closed-door testimony, Sondland stated that he wouldn't have withheld military aid for any reason.

Not only that, he said he didn't recall any conversations with the White House about withholding military assistance in return for Ukraine helping with Trump's political campaign. Even then, though, he left himself some wiggle room, saying a text message he sent to Taylor reassuring him that there was no quid pro was simply what he had heard from Trump.

Weeks later, after testimony from Taylor and National Security Council official Tim Morrison placed him at the center of key discussions, Sondland revised his account in an extraordinary way, saying "I now recall" more details. He amended his testimony to confirm that Taylor's account was correct.

Among the conversations Sondland now recalled was telling an aide to Zelenskiy in September that military aid likely would not occur until Ukraine made public announcements about corruption investigations.

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HOW INVOLVED WAS MULVANEY?

Multiple witnesses describe a cozy relationship between Sondland and Mick Mulvaney, the White House acting chief of staff.

Vindman, a National Security Council official, says Sondland cited a discussion with Mulvaney when pushing Ukrainian officials to open the investigations that Trump wanted into the 2016 presidential election and Biden.

Fiona Hill, another White House national security official, says the then-national security adviser, John Bolton, told her he didn't want to be part of "whatever drug deal Sondland and Mulvaney are cooking up."

Sondland suggests he knows Mulvaney only well enough to wave and say hello.

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TRUMP, REPUBLICANS?

Of the nine witnesses testifying over three days this week, White House officials are concerned most about Sondland — because they aren't sure what he's going to say.

If Sondland's name-dropping is accurate, he may have had direct conversations with Trump.

It'll be hard for the president to attack his own EU ambassador, or for Republicans aware of the president's expectation of loyalty, to do so.

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HOW SONDLAND IS SEEN OVERSEAS

He calls himself a "disruptive diplomat."

Sondland may not be missed on the Continent as he testifies in Washington. Even before he got involved in Ukraine, Sondland's caustic style had already created problems in Brussels, where he is the U.S. ambassador to the 28-nation EU.

He visited Ukraine twice, even though it is not part of the EU and not part of his formal responsibilities. He also gave an interview with Ukrainian television boasting of his closeness to Trump and laying out his views of Ukraine, almost like instructions: "They're Western and they're going to stay Western."

Sondland is known for the grand gesture. At a party for diplomats and journalists last month at the ornate Cercle Gaulois club between the Belgian parliament and royal palace, he highlighted his close links with Trump and the president's confidants. He spoke of a three-hour "family dinner" in Manhattan with two incoming EU leaders, Trump's daughter Ivanka and her husband, Jared Kushner.

There was also a special guest: comedian Jay Leno, who is said to be among Zelenskiy's heroes.

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