Alexandria Ocasio-Cortez is ramping up pressure on her fellow Democrats to begin impeachment proceedings against Donald Trump, saying that she and her colleagues have “a duty” to hold the president accountable.

"We have to move forward on impeachment," Ms Ocasio-Cortez said on Tuesday during an interview with CNN.

She continued, paying respect to speaker of the House Nancy Pelosi, who has so far pushed back on impeachment calls.

“I trust the speaker's taking a measured approach to ensure that we’re moving everyone forward," Ms Ocasio-Cortez said. “Being a speaker is hard, and holding this party together is a difficult task,” she added, “but I think we have to move forward.”

In a separate tweet, Ms Ocasio-Cortez also shot back at arguments that impeachment would be a politically fraught effort with less than two years to go until a presidential election. Not impeaching, she said, is political, too.

“It is just as politicized a manoeuvre to not impeach in the face of overwhelming evidence as it is to impeach without cause,” Ms Ocasio-Cortez wrote.

She continued: “Congress swore an oath to uphold the Constitution. That includes impeachment. We have a duty to preserve our institutions + uphold the rule of the law.”

The statement came in response to a fellow Democrat’s call for impeachment in light of former White House counsel Don McGahn’s decision to refuse a congressional subpoena on Tuesday to testify before the House related to the Mueller report on Russian meddling in the 2016 election.

Mr McGahn is frequently cited in that report saying that Mr Trump attempted to derail the investigation, which has led Democrats to claim the president obstructed justice.

“Stonewalling Congress on witnesses and the unredacted Mueller report only enhances the President’s appearance of guilt, and as a result, he has pushed Congress to a point where we must start an impeachment inquiry,” that Democrat, Mark Pocan, wrote on Twitter.