Treasury Secretary Steven Mnuchin has defended asking to use a government plane for his honeymoon travel this summer, claiming his request was “purely a national security issue.”

As ABC News reported Wednesday, the former Goldman Sachs banker requested the use of a U.S. Air Force jet during his honeymoon travel in France, Italy and Scotland. (Mnuchin married the Scottish actress Louise Linton in June.) According to the report, using such an aircraft could have cost taxpayers as much as $25,000 per hour.

In an interview with Politico Live on Thursday, Mnuchin said his staff made the request so he could have “access to secure communication” throughout his trip.

“This had nothing to do with convenience,” he said. “This was purely a national security issue.”

Mnuchin said that due to spending “over 50 percent” of his time working on national security, he needed a secure communication facility to continue to conduct business while on his honeymoon.

“I speak to, almost on a daily basis, either the president, the secretary of state, the national security adviser, [Defense Secretary] General [James] Mattis,” he said. “We are dealing with, as you know, some of the most complicated issues right now, whether it be North Korea, Iran, Venezuela or anywhere else.”

“At the time my staff wanted to make sure I constantly had access to secure communication and secure information,” he continued. “This was one of the things we explored, so they put in a request to consider the use of an aircraft ― not so much just for flying, but effectively it was a portable office so that I could be available.”

A Treasury spokesperson gave a similar explanation on Wednesday.

Mnuchin said his staff withdrew the request after finding another way to give him access to secure communication channels.

“I’m very sensitive to the use of government funds,” he said.

Mnuchin also claimed the ABC News story about his request was “quite misreported,” but did not specifically dispute any of the details in the report.

Asked on controversy over requesting a government plane for his honeymoon, @stevenmnuchin1 says it was “national security” issue #PROSUMMIT pic.twitter.com/1YQpz6kYms — POLITICO Live (@POLITICOLive) September 14, 2017

It’s unusual for Treasury secretaries to travel on official government planes, due to the high cost of doing so. Such travel is typically reserved for Cabinet members more directly involved in national security matters, such as the defense secretary.

Mnuchin’s request is now under review by the Treasury’s Office of the Inspector General, which already investigating Mnuchin’s trip to Louisville and Fort Knox, Kentucky, last month. During that trip, Mnuchin and Linton flew on an Air Force jet and viewed the solar eclipse.

That trip also sparked controversy, particularly after Linton posted an Instagram showing the couple descending the jet’s staircase and included the names of the high-end designers she was wearing at the time. She also attacked an Instagram user, Jenni Miller of Portland, Oregon, who’d commented on the post criticizing the couple for taking the trip on taxpayer funds. (A Treasury official later clarified that the couple had reimbursed the government for Linton’s transportation expenses.)

“Did you think this was a personal trip?! Adorable!” Linton commented on the now-deleted post. “Do you think the US govt paid for our honeymoon or personal travel?! Lololol.”

Linton later apologized for her response, calling her own post “indefensible.”

“It’s clear that I was the one who was truly out of touch and my response was reactionary and condescending,” she said.

CORRECTION: A previous version of this article incorrectly listed the cost estimate to operate a U.S. Air Force jet as $25,000 per day; that is an estimated hourly cost.