The U.S. continues to take active measures to prepare for the possibility of a nuclear test by North Korea, U.S. officials told NBC News, including the deployment of a special nuclear "sniffer" aircraft, drones, and U-2 spy planes.
The U.S. Air Force's special sniffer plane is capable of detecting evidence of a nuclear explosion.
Two U.S. intelligence officials told NBC News that North Korea is in a position to conduct a nuclear test with little or no warning.
"We expect that they are able to do it at any time, without any real warning," one official said. "They have been engaging in steady preparations."
The officials would neither confirm nor deny that the U.S. has detected signs that a test is imminent.
Three U.S. military officials said the Chinese military is currently on a higher alert as part of a nationwide exercise. The exercise is defensive in nature and not focused on the region near North Korea.
During a Thursday press conference with Italian Prime Minister Paolo Gentiloni, President Trump called North Korea a "menace." He answered a reporter's question about instability in North Korea by praising China's president and China's actions in the region.
"As far as North Korea is concerned, we are in very good shape," said Trump. "I respect [President Xi Jinping] very much, and I think he's working very hard… Some very unusual moves have been made over the past two or three hours and I really have confidence that the president will try very hard."
Watch: Pence in South Korea