Macri cannot attend the session on Thursday because he is out of the country keeping "international commitments," and he will be back in late October, said Patricia Bullrich, president of Macri's Republican Proposal party.

Macri led the country from 2015 to 2019 and is now the leader of Argentina's rightwing opposition.

Judge Martin Bava subpoenaed Macri, 62, last week to testify about his role in the alleged espionage. Macri was in the United States when he got the order to testify.

The sub disappeared in November 2017. When it was found just over a year later, it was at a depth of more than 900 meters (3,000 feet) in a desolate area of the South Atlantic some 400 kilometers (250 miles) off the coast of Argentina.

It had been crushed from an implosion apparently caused by a technical fault. Authorities decided against attempting to refloat it.

Family members of the 44 crew members told investigators they were followed and wiretapped, filmed and intimidated into abandoning any claims related to the incident.

Macri is accused of ordering the espionage. He risks between three and 10 years in jail for allegedly violating Argentina's intelligence laws.

Bava has ordered the indictment of secret service heads Gustavo Arribas and Silvia Majdalani, who reported to Macri at the time.

In March, two former Argentine military chiefs were also sanctioned over the sinking of the submarine.

When he returns to Argentina, Macri will be barred from leaving the country again.