Mnuchin says use of costly gov't jet was necessary for 'secure communications' Mnuchin said travel was necessary for national security purposes.

 -- Treasury Secretary Steven Mnuchin defended his use of a costly government jet to make the short journey from New York City to Washington D.C. following an August meeting in Trump Tower.

When asked about the travel by co-anchor Martha Raddatz on ABC News’ “This Week,” Mnuchin responded that it was necessary for national security purposes.

“There are times when I need secure communications to be in touch with the president and National Security Council,” Mnuchin said. “I had a secure call that day that was critical and set up. It needed to be done at that time, and that’s why I used it.”

Mnuchin also confirmed that his use of the private jet on Aug. 15 is now under review, as are as at least two other requests for government travel involving the secretary.

“The inspector general is reviewing my travel,” Mnuchin replied. “If there’s suggestions we’ll follow it.”

ABC News previously reported on Mnuchin's August trip on a U.S. Air Force C-37 jet, which took less than an hour. Mnuchin was in New York to attend the now-infamous press conference in Trump Tower during which the president made highly controversial remarks on the violence in Charlottesville. Mnuchin and Transportation Secretary Elaine Chao, who also flew on that government jet, flanked the president during his remarks.

The Treasury Department's review of Mnuchin's travel habits was triggered after ethical questions were raised about a military jet he and his wife, Louise Linton, used to travel to Louisville and Fort Knox, Kentucky, in August. It was speculated that they may have used that taxpayer-funded trip to catch a prime view of the solar eclipse.

Investigators are also examining why Mnuchin, an independently wealthy former banker at Goldman Sachs, requested a government jet to take the couple on their European honeymoon in early August, a story first reported by ABC News. Mnuchin has strongly denied he used the Kentucky trip to view the eclipse, and a spokesman for the Treasury Department said the honeymoon request was made so he could communicate securely with Washington. They added that the honeymoon request was later withdrawn.

ABC News' Justin Fishel and Elizabeth McLaughlin contributed to this report.