The United States plans to send a military spy plane to South Korea to detect potential attacks by the North during a global nuclear forum to be held in Seoul later this month, a report said Sunday.

The US and South Korean militaries are discussing deploying a high-flying J-STARS (joint surveillance and target attack system) aircraft during the Seoul Nuclear Security Summit on March 26-27, Yonhap news agency said.

It added that monitoring of the communist North had been strengthened ahead of the forum, which involves more than 50 heads of states including US President Barack Obama.

"Military readiness will be maintained at the highest level to guard against potential attacks via land, sea and the air as well as cyber attacks," Yonhap quoted an unnamed senior Seoul military official as saying.

J-STARS aircraft fly as high as 12 kilometres (7.4 miles) altitude, cruise at Mach 0.8, and can monitor the North's military activities including troop movements, artillery and surface-to-surface missiles.

The aircraft type was deployed in a huge US-South joint military drill held in November 2010 after the North's deadly shelling of a border island.

South Korea says the upcoming summit will focus on ways to safeguard atomic material worldwide and prevent acts of nuclear terrorism.

But the North has blasted the event as an "unsavoury burlesque" intended to justify an atomic attack by South Korea and its ally US.