Donald Trump's motorcade has arrived at the New York State Supreme Courthouse in lower Manhattan.

Court is scheduled to get underway at 10 a.m. ET, with Trump scheduled as the day's only witness.

Donald Trump, in New York, had a prep session with his lawyers Sunday ahead his testimony, sources tell ABC News.

Trump's mood during the session fluctuated between fits of anger regarding the case and being "in a good head space," according to sources.

The former president "can be a good witness if he stays focused," one source said.

Former President Trump is due in court to begin his testimony in his $250 million civil fraud trial at 10 a.m. ET.

Hundreds of members of the news media are huddled outside the New York State Supreme Courthouse ahead of Trump's arrival, with some having waited overnight.

After multiple in-court disputes about communications between him and his law clerk, Judge Arthur Engoron modified his limited gag order to cover attorneys in former President Donald Trump's civil fraud trial.

"Defendants may reference my staff as is appropriate to ask about scheduling issues or the management of the trial, which is an integral part of their jobs. What they may not do is to make any further statements about internal and confidential communications (be it conversations, note passing, or anything similar) between me and my staff," Engoron wrote in his supplemental limited gag order on Friday.

Engoron wrote that defense lawyers Chris Kise, Alina Habba, and Clifford Robert made "repeated, inappropriate remarks about my Principal Law Clerk, falsely accusing her of bias against them and of improperly influencing the ongoing bench trial."

The attorneys have raised multiple arguments during the trial that Engoron and his clerk passing notes between each other suggests impropriety and is distracting. Going forward, if the lawyers want to object to communications with his clerk, Engoron advised that they refer to the order as a "blanket statement."

"This gag order is as narrowly tailored as possible to accomplish its purpose, which is to protect the safety of my staff and promote the orderly progression of this trial," Engoron said.

To justify the safety threat, Engoron added that his chambers has received "hundreds of harassing and threatening phone calls, voicemails, emails, letters, and packages" since the start of the trial,

The judge threatened "serious sanctions" for violations of the extended order.

Lawyers for the New York attorney general, in a late-day court filing, said they support the court-ordered pause on canceling Trump's business certificates -- but warn that a stay of Trump's civil fraud trial would cause a "cascade of delays."

The filing comes more than three weeks after an appeals court, at Trump's request, paused the enforcement of the cancelation of Trump's business certificates that Judge Arthur Engoron had ordered in his summary judgment.

In today's filing, New York Attorney General Letitia James wrote she was "willing to agree to stay enforcement … pending the end of trial and entry of final judgment."

On the other parts of Trump's appeal -- including the request to delay the trial and arguments against Engoron's summary judgment ruling that Trump committed fraud -- James vehemently argued in favor of letting the trial run its course.

"Abruptly halting trial would thus sow chaos and result in an inordinate waste of both public resources and the time and resources of witnesses," James wrote, alleging that Trump is playing courts against one another to create delays.

"Moreover, any delay here would threaten a cascade of delays not only in this case but also in other pending criminal and civil cases against defendant Donald J. Trump," the filing said.

Trump's legal team has until Nov. 9 to submit their reply.