A House Democrat will soon launch an official attempt to impeach President Trump.

Rep. Al Green, a Texas Democrat and member of the Congressional Black Caucus (CBC), is readying the articles of impeachment that mark the first official step in any congressional bid to remove a sitting president.

The articles have little chance of seeing the light of day in a House chamber controlled by Republicans, who have rallied behind Trump amid multiple investigations into ties between Russia and members of the president's inner circle. But Green's gambit highlights the growing apprehension many Democrats have toward the president, and it's sure to energize a liberal base that's sounded the impeachment alarm with increasing volume as the Russian investigation saga has evolved.

Green's criticisms focus on Trump's firing of former FBI Director James Comey, who was leading the administration's probe into Russia's meddling in the 2016 election. Trump had reportedly pressured Comey earlier in the year to drop the investigation into Michael Flynn, Trump's former national security adviser, who was fired after lying about the nature of his conversations with a Russian ambassador.

Comey's firing brought accusations, primarily from Democrats, that Trump may have obstructed an ongoing Justice Department investigation - an impeachable offense, in the eyes of Green.

"The facts are simple and indisputable. The President fired the FBI Director because the Director was investigating the President's campaign connections to Russian interference in the Presidential Election," Green said Tuesday evening in a statement. "This is obstruction of justice."

The episode will be front-and-center on Capitol Hill later this week. Deputy Attorney General Rod Rosenstein, who was critical of Comey and had a hand in his firing, is set to appear Wednesday before the Senate Intelligence Committee. Comey himself is set to appear before the same panel the following day.

It's unclear when Green will officially introduce the articles he's currently drafting. It's also unclear if he'll have any co-sponsors, though Green has not been alone in his calls for impeaching Trump. California Democratic Rep. Maxine Waters, another CBC member, has also beaten that drum.

A spokesman said Green will provide more details Wednesday afternoon, when he's scheduled a press briefing in the Capitol.

Green's effort comes even as Democratic leaders are treading much more lightly in their approach to the Russia-Trump saga. With Trump's approval rating underwater - and new details in the Russia probe emerging almost daily - party leaders sense an opportunity to make huge gains at the polls in 2018 and don't want to overplay their hand. They've tamped down any talk of impeachment, calling instead for the creation of an independent, 9/11-style commission to investigate the Russia inquiry.

"What I've said to members [is] the only thing that matters are the facts - the facts and the law," House Minority Leader Nancy Pelosi (D-Calif.) said Tuesday on CNN's "New Day" program, when asked about impeachment. "That's what [an] investigation will reveal to us."

Green has rejected that argument, contending that Trump's actions have already risen to a level demanding congressional intervention.

"This will remain obstruction of justice regardless of the findings of any investigation," he said.

"Obstruction of justice by the President is the problem," he added. "Impeachment by Congress is the solution."