"I didn't try to wrest control of the irregular channel," says Acting Ukraine Ambassador William Taylor.

"Both channels were interested in having a meeting between President Zelensky and President Trump," he says.

But he says he did not know that the "irregular channel" - referring to Gordon Sondland, Rick Perry and Kurt Volker - were also tying US military assistance to such a meeting.

US Ambassador to the EU Gordon Sondland has been a key name in Wednesday's hearings. He's testified - and added to that testimony since.

The BBC's Jon Sopel explains the significance in 60 seconds.

Both US officials testifying today say they know nothing about Hunter Biden's background or why he was hired by Ukrainian energy firm Burisma.

"I have no idea what Hunter Biden studied in university or what his CV says," says George Kent.

Republicans had asked to interview Hunter Biden, but Democrats on the committee blocked that request.

Image source, Paul Morigi/Getty Images

Image source, Getty Images

A spokesman for Democratic presidential hopeful Joe Biden says he is not watching today's hearing.

"[The] House is doing their job. He’s doing his: beating Trump," the spokesman said.

Biden is meeting with labour union leaders today. Donald Trump - who has been hosting President Erdogan of Turkey - also said he had better things to do than watch the hearing.

The Republicans have continued to draw attention to the fact they haven't been able to question the witnesses they want - particularly in connection with the Bidens and Ukraine. Here's what we know about this issue.

The Republicans on the committee are upset that Democratic Chairman Adam Schiff interrupted the Republicans' 45 minutes of questions with a point of order.

Republican John Ratcliffe asked if he should interrupt every time he disagrees with the nature of Democrats' questions.

After Democrats and Republicans briefly clash over the rules, cameras cut back to a clearly confused Ambassador Taylor.

Taylor tells lawmakers: "In 2016 candidate Trump made a statement saying that it was possible that he would allow Crimea to go back to Russia.

"That sentiment is amazingly inflammatory to all Ukrainians."

Image source, Drew Angerer/Getty Images

In a closed-door meeting with her Democratic colleagues on Wednesday, House Speaker Nancy Pelosi said President Trump "must be held accountable", US media report.

"This is a very serious event in our country. We wish it could have been avoided. None of us came here to impeach a president," she is quoted as saying.

It's now the Republicans' turn to question the witnesses.

Devin Nunes begins by claiming Democrats "downplay, ignore, and outright deny the many accusations that the Ukrainians did meddle in the election" and that President Trump could rightfully have wanted to know more about the problem.

These interference accusations are unsubstantiated.

The BBC's Jonah Fisher in Kyiv looks at how Ukraine became caught up in US political wranglings earlier this year. Read the full analysis here.

Top diplomat Bill Taylor: "To withhold that assistance for no good reason other than help with a political campaign made no sense."

President Trump has just made remarks to reporters to the Oval Office where he is hosting Turkish President Recep Tayyip Erdogan.

Mr Trump said he hasn't been watching the impeachment hearing.

"I'm too busy to watch it," he says."It’s a witch hunt, it’s a hoax."

He said he had not been briefed on it yet, either.

"There's nothing there," he says.

The Democratic counsel also questioned Kent on unsubstantiated allegations about Ukrainian interference in the 2016 election that the president reportedly wanted investigated.

Kent said that to his knowledge, "there is no factual basis" that Ukraine interfered.

When asked who did interfere in the 2016 US presidential election, Kent answered: "I think it's amply clear that Russian interference was at the heart of the interference."

Acting US Ambassador to Ukraine Bill Taylor testified that one of his aides had overheard a call between US Ambassador to the EU Gordon Sondland and Trump.

In that call, Taylor says his aide heard Trump directly asking his ambassador about "investigations" in Ukraine.

This appears to tie the request for an investigation into the Bidens directly to Trump. The overheard call had not been previously disclosed in Taylor's earlier testimony.

Image source, Bright Line Watch

Political analysis taking part in an initiative called Bright Line Watch, external have rated the president's conduct related to Ukraine as both one of the most "abnormal and important events" during his time in the White House.

• SIMPLE GUIDE:A basic take on what's going on
• GO DEEPER:Here's a 100, 300 and 800-word summary of the story
• WHAT'S IMPEACHMENT?A political process to remove the president
• VIEW FROM TRUMP COUNTRY:Hear from residents of a Virginia town
• ON THE DOORSTEP: A Democrat sells impeachment to voters

Image source, Andrew CABALLERO-REYNOLDS / AFP

Some of Bill Taylor's testimony includes second-hand information: retelling things that Ambassador Gordland Sondland and Tim Morrison, Eurasia expert on the National Security Council staff, told him about meetings and actions taken by President Trump.

But BBC's Anthony Zurcher explains that Taylor has first-hand information of "Ukrainian fears that they were being pulled into US domestic politics".

Image source, Union Pub

Several impeachment themed cocktails are on offer around Washington today.

Bartenders are serving "subpoena coladas" and other cocktails that use peach flavoring as an ingredient - such as "Impeachment Please" and "I Got 99 Problems but Impeachment Ain't One".

Robin Webb, the owner of a local beer garden, tells the Hill newspaper that he keeps a large bottle of champagne in a cabinet labeled: "In case of President Pelosi, break glass."

Taylor says Sondland described Trump as a businessman "about to sign a cheque to someone who owes him something".

But Taylor argued Ukrainians did not owe Trump anything, though the president "had a feeling of having been wronged by the Ukrainians". The Democrats' counsel clarifies that what was "owed" would be investigations into the Bidens and alleged interference in the 2016 elections.

"To fix the wrong, exactly," Taylor confirms.

A new video is just out from the White House, in which Trump vows to "drain the swamp".

"It's all very simple. They're trying to stop me because I'm fighting for you," he says.

Trump is meeting with Turkish President Recep Tayyip Erdogan at the White House.

Image source, Jim Lo Scalzo-Pool/Getty Images

Taylor says Ambassador Sondland told him that Trump wanted President Zelensky to "state publicly that Ukraine will investigate Burisma and alleged Ukrainian interference in the 2016 US election".

Sondland also told Taylor "everything" regarding Ukraine was dependent on a public announcement of this investigation - including security assistance.

According to Taylor, Sondland also informed Zelensky that "if President Zelensky did not 'clear things up' in public, we would be at a 'stalemate.'"

"I understood a 'stalemate' to mean that Ukraine would not receive the much-needed military assistance," Taylor says.