WASHINGTON (AFP) - US President Donald Trump has accepted the invitation from House Speaker Nancy Pelosi to deliver his state of the union speech on Feb 4, the White House said on Friday (Dec 20).

The invite for the annual presidential speech to Congress comes at a charged political moment, with Trump freshly impeached for abuse of power and obstruction of Congress, and facing a trial in a US Senate that is almost certain to acquit him.

It sets up a potentially explosive encounter between Trump and Pelosi, his chief Democratic nemesis in Congress and the woman who launched the formal impeachment inquiry.

Pelosi is now at odds with the Senate's Republican leadership about the parameters of the impeachment trial.

"In the spirit of respecting our Constitution, I invite you to deliver your State of the Union address before a Joint Session of Congress on Tuesday, Feb 4, 2020," Pelosi wrote to the president in a letter.

Trump "has accepted the Speaker's invitation," White House spokesman Hogan Gidley said.

Pelosi's three-paragraph letter also highlighted the system of separation of powers that was created by the framers of the US Constitution: "three co-equal branches acting as checks on each other."

The reference is notable, given that Democrats accuse Trump of seeking to block Congress' powers to oversee the executive branch by refusing to cooperate with the impeachment probe.

The speech will take place in the US House of Representatives, the very chamber that impeached him on Wednesday.

During the 2019 state of the union, the speaker appeared to mock Trump with an exagerated clap that was quickly interpreted online as sarcasm.

She stood up during a round of applause and pointed her outstretched hands directly at the president, pursing her lips and looking right at him as she clapped.

Their relationship has soured further since then.

On the eve of his impeachment, Trump wrote a furious six-page letter to the speaker, wildly accusing her of "declaring open war on American Democracy."

Pelosi, launching the impeachment debate on Wednesday, said Trump posed an "ongoing threat" to the country's security that left Democrats "no choice" but to impeach him.