It accused Lee's conservative government of using "nonexistent nuclear and missile threats" from the North as a pretext for an invasion.

With tensions rising to their highest level in more than a decade, a separate commentary carried by KCNA also warned the US and South Korea against holding joint military exercises.

It said the two countries would pay a "high price" for conducting what it described as "war preparations".

The warning comes as the US and South Korean armed forces announced the annual "Key Resolve/Foal Eagle" drill would take place from March 9-20 across the peninsula.

Missile test

Clinton is due in Seoul on Thursday night on the third stop of her Asia tour [GALLO/GETTY]
At the same time South Korean officials and media reports have said the North is preparing to test fire longest-range missile, the Taepodong 2.

On Wednesday Lee Sang-Hee, South Korea's foreign minister, said the missile could be ready for launch within two or three weeks and warned the North any test would be seen as a "grave provocation".

Clinton, speaking in Japan earlier this week, has said any missile test would be "very unhelpful" for US-North Korean relations and has urged Pyongyang to tone down its rhetoric.

The Taepodong 2 is thought to be theoretically capable of hitting targets as far away as the US west coast, although it has never flown successfully.

Clinaton has previously said the US government would normalise diplomatic relations with the North if the isolated nation were to "completely and verifiably eliminate" their nuclear weapons programme.

Six party talks between North and South Korea, China, Japan, Russia and the US aimed at restricting North Korea's atomic programmes in exchange for economic and diplomatic incentives began in August 2003 but stalled in December 2008.

Last month, the North announced it was scrapping all agreements with the South, including a 1991 pact that recognised the Northern Limit Line (NLL), a sea border drawn unilaterally by US-led United Nations forces after the 1950-1953 Korean war.

The border has twice been the scene of deadly naval clashes in 1999 and 2002.

The North has never recognised the NLL and although the line has served as a de facto border, North Korea has frequently demanded it be redrawn - a move the South has rejected.