New York, New York - The lawyer who negotiated a hush money payment from Donald Trump to an adult film star was grilled on Thursday by the former US president's defense attorney, who suggested his activities bordered on "extortion."

Trump is accused of falsifying business records to reimburse his lawyer, Michael Cohen, for a $130,000 payment to X-rated movie actress Stormy Daniels just days ahead of the 2016 election against Hillary Clinton.

The trial resumed on Thursday after a day off on Wednesday, with prosecutors urging Judge Juan Merchan to fine the Republican presidential candidate for violating a gag order he imposed to protect trial participants.

After hearing arguments from both sides, the judge, who held Trump in contempt and fined him $9,000 on Tuesday for gag order violations, said he would issue a ruling later.

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Keith Davidson, Daniels' former attorney, then took the witness stand to continue his testimony as Trump sat at the defense table.

After prosecutors wrapped up their questioning, Trump's attorneys began their cross-examination of Davidson, who also represented another woman, Karen McDougal, who claimed to have had a year-long affair with Trump.

Emil Bove, one of Trump's lawyers, began his questioning, which quickly turned heated, by asking Davidson if he was familiar with the laws about extortion.

"When you were negotiating on behalf of McDougal and Daniels one of your concerns was staying on the right side of the law with regard to extortion," Bove said.

"I suppose so," Davidson replied. "I did everything I could to make sure my activities were lawful."

Prosecutors earlier walked Davidson through the negotiations with Cohen about the hush money payment and damage control efforts after media reports emerged in January 2018 about Daniels' 2006 sexual encounter with Trump.

At the time, Daniels initially denied that she had ever had an "affair" with Trump or received hush money from him.

She has since recanted, saying that this prior statement was not true and that she did indeed have sex with the married Trump at a celebrity golf tournament in Lake Tahoe in 2006.

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"[Cohen] wanted her to deny the story to protect his client," Davidson said.

He added that Coehn had threatened to "rain legal hell down" on Daniels.