The jury deliberating in Harvey Weinstein's rape trial indicated on Friday that it is deadlocked on the most serious charges.

In a note sent to the judge during their lunch break, jurors posed a question asking if it were permissible for them to be hung on two counts of predatory sexual assault while reaching a unanimous verdict on other charges.

After consulting with prosecutors and Weinstein's lawyers, Judge James Burke told the jury of seven men and five women to keep working towards a unanimous verdict on all charges and sent them back to continue deliberating.

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Weinstein's lawyers said they would accept a partial verdict, but prosecutors said no and Burke refused to do so.

The jury, in its fourth day of deliberations, has been particularly focused on the key aspect of both predatory sexual assault counts: The Sopranos actress Annabella Sciorra's allegations that Weinstein raped and forcibly performed oral sex on her in the mid-1990s.

Jurors started the day on Friday by listening to a reading of Sciorra's cross-examination and follow-up questioning by prosecutors. About 90 minutes into the reading, the jurors notified the judge they had "heard enough" and resumed their deliberations.

Sciorra testified nearly a month ago. She was the first accuser to testify in the closely watched trial.

The jury has already focused on emails that Weinstein sent regarding Sciorra, including ones to the private Israeli spy agency he allegedly enlisted to dig up dirt on would-be accusers as reporters were working on stories about allegations against him in 2017.

Sciorra, now 59, was the first accuser to testify and took the witness stand nearly a month ago, telling jurors how the once-powerful movie mogul showed up unexpectedly at the door to her Manhattan apartment before barging in and raping and forcibly performing oral sex on her in late 1993 or early 1994.

On cross-examination, Sciorra was grilled about why she opened her door in the first place and did not find a way to escape if she was under attack.

Weinstein lawyer Donna Rotunno asked: "Why didn't you try to run out of the apartment? Did you scratch him? Try to poke him in the eyes?"

Actor Annabella Sciorra arriving at court to testify as a witness in the case of film producer Harvey Weinstein in New York City, New York, US [Lucas Jackson/Reuters]

Prosecutors say Sciorra weighed only about 110 pounds (50kg) in those days, making her no match for the 300-pound (136-kg) Weinstein.

"He was too big" to fight off, she told the jury. "He was frightening."

Weinstein, 67, is charged with five counts stemming from the allegations of Sciorra and two other women - an aspiring actress who says he raped her in March 2013 and a former film and TV production assistant, Mimi Haleyi, who says he forcibly performed oral sex on her in March 2006.

Sciorra's accusations are key to the most serious charges that jurors are weighing in the case - two counts of predatory sexual assault, which carry a maximum penalty of life in prison.

The charge requires prosecutors to show that a defendant committed a prior rape or other sex crime, but does not have the statue of limitation constraints that would bar her allegations from consideration on their own.

Film producer Harvey Weinstein listening to testimony being read back during jury deliberations in his sexual assault trial [Jane Rosenberg/Reuters]

Weinstein has maintained any sexual encounters were consensual.

Sciorra went public in a story in The New Yorker in October 2017 after one of the few people she says she told about the incident, actress Rosie Perez, got word to reporter Ronan Farrow that he should call her.

Sciorra did not get involved in the criminal case until later. Her allegations were not part of the original indictment when Weinstein was arrested in May 2018, but after some legal shuffling, they were included in an updated one last August.

Weinstein's lawyers fought to get her removed from the case in the run-up to the trial, arguing to no avail that prosecutors shouldn't be allowed to use her claims because they predated the enactment of the predatory sexual assault charge in 2006.

Weinstein's lawyers have also argued that it is plainly unfair to make the producer defend himself against something alleged to have happened more than a quarter-century ago. They contend prosecutors shoehorned Sciorra into the case to get a marquee name on the witness stand.

"Annabella was brought into this case for one reason and one reason only," Rotunno said in her closing argument last week. "She was brought in so there would be one witness who had some star power, one witness you may recognise and one witness whose name may mean something."