President Donald Trump pressed then-Secretary of State Rex Tillerson to help persuade the Justice Department to drop a criminal case against an Iranian-Turkish gold trader who was a client of Rudy Giuliani, according to three people familiar with the 2017 meeting in the Oval Office.

Tillerson refused, arguing it would constitute interference in an ongoing investigation of the trader, Reza Zarrab, according to the people. They said other participants in the Oval Office were shocked by the request.

Tillerson immediately repeated his objections to then-Chief of Staff John Kelly in a hallway conversation just outside the Oval Office, emphasizing that the request would be illegal. Neither episode has been previously reported, and all of the people spoke on condition of anonymity due to the sensitivity of the conversations.

The White House declined to comment. Kelly and Tillerson declined to comment via representatives. Another person familiar with the matter said the Justice Department never considered dropping the criminal case.

Zarrab was being prosecuted in federal court in New York at the time on charges of evading U.S. sanctions against Iran's nuclear program. He had hired former Attorney General Michael Mukasey and Giuliani, who has said he reached out repeatedly to U.S. officials to seek a diplomatic solution for his client outside the courts.

The president's request to Tillerson -- which included asking him to speak with Giuliani -- bears the hallmarks of Trump's governing style, defined by his willingness to sweep aside the customary procedures and constraints of government to pursue matters outside normal channels. Tillerson's objection came to light as Trump's dealings with foreign leaders face intense scrutiny following the July 25 call with Ukraine's president that has sparked an impeachment inquiry in the House.

The episode is also likely to fuel long-standing concerns from some of Trump's critics about his policies toward Turkey and his relationship with its authoritarian president, Recep Tayyip Erdogan. Zarrab's release was a high priority for Erdogan until the gold trader agreed to cooperate with prosecutors in New York.