(CNN) Nearly a month after waiting for House Speaker Nancy Pelosi to transmit the articles of impeachment, the White House and President Donald Trump's legal team are readying for the next phase of the impeachment process.

"We've been prepared since before Christmas. And we remain prepared," a White House official said, noting that the White House has done all it can to prepare for the Senate trial while waiting for the House to name its impeachment managers. The White House is still deciding exactly who will make up the legal team defending the President during the trial.

The expected House vote this week to name its impeachment managers and transmit the articles to the Senate will kick off a process that will see the White House issue its first official legal response to the President's impeachment, likely by the end of the week.

After the House vote, as part of the opening of the trial, the Senate will send a summons to the President asking him to appear, which the President's legal team will answer as a formality, a source close to the team told CNN. In its response, the legal team is likely to argue that the impeachment charges do not rise to the level of "high crimes and misdemeanors." The President is not expected to appear but can be represented by his attorneys.

But the meat on the bones of the President's defense will come in the form of a trial brief, which will address key legal arguments of the President's defense and the legal issues at stake, the source said. That document is already largely completed and will likely be submitted within two days of the House vote to transmit the articles of impeachment to the Senate.

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