Tensions remain high on the Korean Peninsula amid reports the US has deployed an unmanned spy plane to Japan to boost its surveillance after North Korea readied missile launchers on its east coast.
The Global Hawk will be stationed at the US airbase in Misawa, northern Japan, in the first ever deployment of the aircraft in the country, the Sankei Shimbun reported, quoting government sources.
The US military informed Japan last month about plans to deploy the plane between June and September but has brought the date forward, reports Sky News.
It comes after North Korea warned foreign diplomats they may not be safe in the country if war breaks out.
Pyongyang asked foreign embassies whether they were considering evacuating staff, saying the government could not guarantee their safety in the event of conflict from April 10.
The British Foreign Office dismissed the warning as "rhetoric".
However, an urgent international effort to defuse the situation is under way.
The heads of EU missions are to meet to hammer out a common position on the crisis, while the US works its diplomatic channels to resolve the stand-off with Pyongyang.
US Secretary of State John Kerry has been holding talks with officials in South Korea, as well as China - historically North Korea's ally - to see if the Chinese can put any more pressure on North Korean leader Kim Jong-Un to back down.
Reporting from the South Korean capital Seoul, Sky's Asia Correspondent Mark Stone, said: "In the skies above the Korean Peninsula there are spy planes operating.
"There will be drones - American drones - operating before long from a base in Japan.
"They are trying to get as much of a sense as possible of what it is that Kim Jong-Un is doing on the ground with his weaponry.
"We know he has some pretty sophisticated weaponry.
"There are artillery rounds just over the border. They could in theory hit Seoul. That's a big concern for South Korea.
"That's why they are trying to put these intelligence reports together, as well as the diplomacy behind the scenes, to try and work out what Kim Jong-Un might be up to."