US House Speaker Nancy Pelosi has announced that the House of Representatives is moving forward to draft articles of impeachment against President Donald Trump.

“Our democracy is what is at stake,” Ms Pelosi said. “The president leaves us no choice but to act.”

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Ms Pelosi delivered the historic announcement as Democrats push toward a vote, possibly by Christmas.

She said she was authorising the drafting of articles of impeachment “sadly but with confidence and humility”.

“The president’s actions have seriously violated the Constitution,” Ms Pelosi said.

At the heart of the impeachment probe is a July call with the president of Ukraine, in which Mr Trump pressed the leader to investigate Democrats as Trump was withholding aid to the country.

However, following the announcement, the president accused Democrats of trying to impeach him over “two totally appropriate (perfect) phone calls with the Ukrainian President”.

“The Do Nothing, Radical Left Democrats have just announced that they are going to seek to Impeach me over NOTHING,” the president tweeted.

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“They already gave up on the ridiculous Mueller “stuff,” so now they hang their hats on two totally appropriate (perfect) phone calls with the Ukrainian President….

“This will mean that the beyond important and seldom used act of Impeachment will be used routinely to attack future Presidents. That is not what our Founders had in mind.”