Four days after ordering the assassination of the second most powerful military figure in Iran, the most pressing issue on President Donald Trump's mind is his own impeachment.

"The Impeachment Hoax, just a continuation of the Witch Hunt which started even before I won the Election, must end quickly," Trump tweeted on Monday. "Read the Transcripts, see the Ukrainian President's strong statement, NO PRESSURE - get this done. It is a con game by the Dems to help with the Election!"

The president's tweet comes as the House of Representatives continues withholding the articles of impeachment against Trump from the Senate as Democrats push for a fair and impartial trial.

It also comes as Trump faces a rapidly escalating firestorm over his decision to unilaterally order the strike against Qassem Soleimani, setting off a high-stakes conflict with Iran that could result in it acquiring a nuclear weapon.

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Four days ago, President Donald Trump ordered an airstrike that killed Iran's most powerful military general, Qassem Soleimani, setting off a high-stakes conflict with the rogue regime that could result in it acquiring a nuclear weapon.

On Monday, the president was preoccupied not with the potential consequences of assassinating one of the most highly revered figures of a sovereign nation, but with his own impeachment.

"The Impeachment Hoax, just a continuation of the Witch Hunt which started even before I won the Election, must end quickly," Trump tweeted. "Read the Transcripts, see the Ukrainian President's strong statement, NO PRESSURE - get this done. It is a con game by the Dems to help with the Election!"

The House of Representatives last month passed two articles of impeachment against Trump. The first charged him with abuse of power and the second with obstruction of Congress.

Both articles relate to Trump's efforts to strongarm Ukraine into delivering political dirt on former Vice President Joe Biden while withholding vital military aid and a White House meeting that Ukrainian President Volodymyr Zelensky desperately sought.

The "Transcripts" Trump mentioned in his tweet refer to documents the White House released of two of Trump's phone calls with Zelensky. One of them was a transcript of Trump's first call with Zelensky in April, shortly after he was elected president in Ukraine. The second was a memo — not a transcript — of Trump's second phone call with Zelensky on July 25.

The White House's memo, witness testimony, and Trump's own public statements confirmed that he asked Zelensky multiple times during the July 25 call to investigate Biden, as well as a bogus conspiracy theory suggesting Ukraine interfered in the 2016 election to help Democrats.

The president froze a nearly $400 million congressionally appropriated military aid package to Ukraine shortly before the phone call.

In the months since, a cascade of testimony from career foreign-policy and national-security officials who worked for Trump showed that the phone call was just one data point in a months-long campaign, spearheaded by Trump's personal lawyer Rudy Giuliani, to force Ukraine to accede to Trump's personal and political demands.

House Speaker Nancy Pelosi said she will withhold the articles of impeachment from the Senate until the Republican-controlled upper chamber commits to a trial that is fair and impartial to Democrats.

Trump has repeatedly said, as he did in his tweet on Monday, that the House is withholding the articles in an effort to delay impeachment proceedings and help Democrats' election chances in November.

The president's tweet comes in the middle of a firestorm surrounding his decision to have Soleimani assassinated.

Secretary of State Mike Pompeo said Trump ordered an airstrike because of "imminent threats to American lives."

The Pentagon also called the strike a "defensive" action, and Trump said he gave the order to "stop a war," not start one.

When Pompeo was asked about the "imminent threats" during a CNN interview on Friday morning, the secretary of state said he couldn't go into many details but said the drone strike saved American lives.

"These were threats that were located in the region [of Iraq]," Pompeo said, when he was pressed on whether there was any imminent threat to the US homeland.

But a series of revelations since have raised questions about whether there was an imminent threat, as Pompeo and others have said, and how robust the underlying evidence supporting the strike actually was.

"Even if these imminent attacks were planned, it's just odd, because if that was the case, that means there were cells in Iraq that were ready to attack us, throughout the country, apparently," Brett McGurk, a veteran diplomat who served as the Special Presidential Envoy for the Global Coalition to Counter ISIL, told MSNBC's Nicolle Wallace.

"Soleimani wasn't going to carry out those attacks himself. I assume those cells are still in place," he said. "So it's a very volatile situation, the Iranians will react, and then the onus will be back on the United States for what we do. The capabilities are there, they've been there for a long time. So removing Soleimani does not necessarily remove that threat at all."

"An imminent threat is what you would need to justify taking an action in self-defense," Oona Hathaway, a professor of international law at Yale University and a former national security lawyer in the Defense Department's Office of General Counsel, told the Washington Post.

Although the Trump administration has repeatedly used the phrase "imminent threat" in the days since announcing the airstrike, Hathaway noted that it wasn't used in the Pentagon's initial statement on the matter.

"It makes me wonder whether the lawyers realized that they had a problem on their hands," she told the Post.

Additional reporting from The New York Times' Rukmini Callimachi indicated that even the underlying intelligence the Trump administration has cited as necessitiating the strike against Soleimani is "razor thin."

"No one's trying to downplay Suleimani's crimes," Callimachi said. "The question is why now? His whereabouts have been known before. His resume of killing-by-proxy is not a secret. Hard to decouple his killing from the impeachment saga."