President Donald Trump called the bank and tax fraud trial of his former campaign chairman Paul Manafort (above) "very sad". Picture: Reuters/Jonathan Ernst

Alexandria - Weighing in even as a Virginia jury deliberates for a second day, President Donald Trump on Friday called the bank and tax fraud trial of his former campaign chairman Paul Manafort "very sad" and described the defendant a "very good person."

Manafort's trial in federal court in Alexandria is the first stemming from Special Counsel Robert Mueller's 15-month-old investigation of Russia's role in the 2016 US election.

Trump has called Mueller's investigation, which had cast a cloud over his presidency, a "rigged witch hunt."

"I think the whole Manafort trial is very sad, when you look at what's going on there. I think it's a very sad day for our country," Trump told reporters at the White House.

"He worked for me for a very short period of time. But you know what? He happens to be a very good person. And I think it's very sad what they've done to Paul Manafort."

Trump made his comments while the jury of six women and six men were deliberating behind closed doors on Friday morning. The jurors met for about seven hours on Thursday without reaching a verdict on 18 criminal counts Manafort is charged with.

The charges largely predate Manafort's five months working on Trump's campaign during a pivotal period in the 2016 presidential race, including three months as campaign chairman.

Manafort, 69, faces five counts of filing false tax returns, four counts of failing to disclose his offshore bank accounts and nine counts of bank fraud. If convicted on all counts, he could spend the rest of his life in prison.

Jurors in the trial are not sequestered but have been instructed not to watch news reports or talk to others about the matter.

"I think we are optimistic the case might end soon with some sort of verdict," Judge T.S. Ellis said in open court after the jury resumed deliberations on Friday morning.

The judge made the comment before telling spectators including journalists that he did not want them running out of the courtroom while the jury announces its verdict on the various counts. He did not indicate he had inside knowledge of their deliberations.

The jury, deliberating in a room at the federal courthouse in Alexandria, sent a note on Thursday afternoon asking Ellis four questions including one about defining "reasonable doubt." In a criminal case, a jury must find a defendant guilty "beyond a reasonable doubt."

The question suggested one or more jurors may be grappling with whether prosecutors met this standard of proof on certain counts.

"The fact that they are sending questions on reasonable doubt tells me that the group is divided," jury consultant Alexandra Rudolph said. "There is at least one juror who has not decided the case and who is not convinced."

While the general rule is that juries reach verdicts on Friday to avoid having to return after a weekend, Rudolph said she believed it was likely these deliberations will carry over into early next week.

The jurors also asked Ellis about when someone must disclose a foreign bank account to the Treasury Department, about the definition of a "shelf company" - an inactive company often sold to people aiming to bypass the registration process - and about the exhibit list.

Prosecutors accused Manafort of hiding from US tax authorities $16 million in money he earned as a political consultant for pro-Russian politicians in Ukraine to fund an opulent lifestyle and then lying to banks to secure $20 million in loans after his Ukrainian income dried up and he needed cash.

The judge said he received a motion Thursday night from a group of news organisations seeking to unseal parts of the proceedings that he had kept from becoming public. Ellis said he would allow lawyers for the media outlets to argue the motion on Friday afternoon.