The United States is close to deploying an advanced unmanned spy plane over South Korea which could provide a much more detailed view of North Korea's military activities, a report said.

The US military newspaper Stars and Stripes said Washington is negotiating with Seoul to fly a Global Hawk drone near the Demilitarised Zone (DMZ) separating the two Koreas.

"I think we are very close," the paper quoted Lt. Col. Terran Reneau, chief of intelligence, surveillance and reconnaissance for the 13th US Air Force in Hawaii, as saying.

Another air force officer, Lt. Col. David Gerhardt, was quoted as saying in the article published Monday that the Global Hawk "will likely fly over land in Korea as soon as agreements have been solidified to do that".

South Korean defence ministry spokesmen could not immediately be reached for comment.

The United States, which bases 28,500 troops in the South, already keeps watch over the North with satellites and piloted U-2 spy planes.

The Global Hawk can stay in the air longer, flying at an altitude of about 20 kilometres (12 miles) for up to 40 hours, with a line of sight to targets some 550 kilometres away.

This means that a drone flying just south of the DMZ could keep watch over all North Korea and over Chinese territory north of the Yalu border river.

The deployment could provide an "unprecedented view of goings-on in reclusive North Korea and draw the ire of China", Stars and Stripes said.

The Hawks carry long-range and infrared cameras, radar and listening devices that can intercept foreign military signals.

North Korea tested nuclear weapons in 2006 and 2009 as well as long-range missiles in 1998, 2006 and 2009, incurring United Nations sanctions.

Inter-Korean relations have been tense since Seoul accused Pyongyang of torpedoing a warship in March 2010 with the loss of 46 lives.

The North denied involvement in the sinking but shelled a South Korean border island last November, killing four people.