A United States federal prosecutor said his office is hashing out a plea deal to a Quebec woman accused last year of sending poison to former president Donald Trump.

Pascale Ferrier is charged with threatening to kill and injure the US president, sending threats through the mail and violating biological weapons prohibitions.

She sent a letter containing the poison ricin that was mailed to the White House.

Ferrier also faces 16 federal charges in Texas related to letters containing ricin sent to law enforcement officials in that state.

David Bos, a public defender representing Ferrier, said the charges in Texas would also be part of plea negotiations.

Ferrier made a brief appearance in a Washington DC court Thursday morning by video, reported CP24, where Prosecutor Michael Friedman told the court he discussed a possible plea deal with other Justice Department officials.

Friedman outlined the potential offer to Ferrier's defence lawyer.

Her case is due back in court on November 10.