The United States is playing down the threat of war on the Korean peninsular, following weeks of bellicose statements from North Korea.
The US earlier confirmed it would deploy a missile defence system to the Pacific island of Guam, after threats that Pyongyang would target the US military base there.
But Washington says the latest rhetoric does not suggest war is imminent.
Responding to South Korean reports that the North has moved two mobile rocket launchers to its east coast, White House spokesperson Jay Carney said the US wouldn't be surprised if North Korea launched a test missile, as it has done in the past.
The US, like other countries, has also chosen not to act on North Korea's fresh warning that it would be unable to protect foreign embassies in the event of conflict.
British diplomats said on Friday the North had asked them to respond by 10 April on what support the embassy would need in the event of any evacuation.
The North has also announced a formal declaration of war on the South and pledged to reopen a mothballed nuclear reactor.
North Korea shelled a South Korean island and killed four people in 2010. A South Korean corvette was also previously sunk
Castro asks North Korea and US to avoid war
Meanwhile former Cuban leader Fidel Castro has called for North Korea and the United States to avoid hostilities.
In a newspaper column published in state media on Friday, Castro, 86, said that if war breaks out the people of both North and South Korea will be sacrificed.
He said that while North Korea has demonstrated its technical and scientific achievements, she also had a duty to the countries which have been her friends.
He also said it is the duty of the United States to avoid a clash.
Cuba is one of the last remaining allies of the communist government in Pyongyang.
"The Democratic People's Republic of Korea was always friendly with Cuba, as Cuba has always been and will continue to be with her," Castro wrote.