U.S. Defense Secretary James Mattis flew to the heavily fortified border with North Korea in a Black Hawk helicopter when he visited Seoul last week, the New York Times reported last Friday.

"Mattis's copter circled the hills and flatlands that dot the densely packed region. He flew over a succession of high-rise residential complexes and surveyed armored tank positions," the paper said.

Mattis flew to the border truce village of Panmunjom right after arriving in South Korea.

"The defense secretary took 30 minutes, by Black Hawk helicopter, to get to the border, though the trip could have easily been done in 10, so short is the distance," the daily added.

Analysts say the trip suggests that the U.S. is preparing for a possible emergency on the Korean Peninsula, but Mattis has said Washington's aim is not war but denuclearization of the peninsula.

