The tumult in Washington has deepened over allegations that US President Donald Trump had sought to end the FBI's investigation into ties between his first national security aide and Russia.
Democrat congressman from Texas Al Green, on Wednesday called for the impeachment of US President Donald Trump on the floor of the House of Representatives.
He become the first Member of Congress to have made such a call on the house floor.
Green said Trump obstructed justice by sacking FBI director James Comey, who was investigating possible Russian influence during the 2016 US election.
Vote for independent commission
Democratic lawmakers on Wednesday said they would try to force a vote in the US House of Representatives on forming an independent commission to investigate possible Russian influence during last year's election which saw Trump take office.
They said Republicans could not be trusted to thoroughly investigate Trump.
"Speaker (Paul) Ryan has shown he has zero, zero, zero appetite for any investigation of President Trump," Representative Elijah Cummings told a news conference.
He charged the White House with obstructing congressional investigations and refusing to provide documents.
Cummings and Eric Swalwell introduced a bill in December 2016 and again in January 2017 seeking to establish a 12-member, bipartisan-appointed, independent commission to investigate.
Democrats have been pushing for a special prosecutor or independent investigation of Russia and the election, and possible links between the Trump's associates and Moscow as the Republican campaigned for president.
Russia has denied that it sought to meddle in the US vote.
The Republican leaders of the House have not allowed the legislation to move forward, forcing Democrats to use a parliamentary procedure known as a "discharge petition" aimed at forcing a vote on legislation that would create the commission.
So far, Representatives Walter Jones and Justin Amash are the only two Republicans in the House to support the petition, which would not succeed unless 23 members of their party to join all 193 Democrats in signing it.
Democrats have used discharge petitions successfully only twice in recent years, most recently for a vote to preserve the export-import bank in 2015.
The tumult in Washington deepened on Tuesday over allegations Trump had sought to end the FBI's investigation into ties between Trump's first national security adviser, Michael Flynn, and Russia.
Last week Comey was fired by Trump, triggering a political firestorm.
Comey wrote a memo detailing Trump's comments to him in February saying "I hope you can let this go," referring to the Flynn probe, according to a source who has seen a memo written by Comey.
The Comey memo caused alarm on Capitol Hill and raised questions about whether Trump attempted to interfere with a federal investigation.
The White House denied the report, saying it was "not a truthful or accurate portrayal of the conversation between the president and Mr. Comey."