The Defence Department in Washington said the reinforcements would act as a deterrent against any North Korean aggression, in the event that the US goes to war on Iraq
Among the possible moves are the deployment of additional bombers to the island of Guam and fighter planes to Japan.
American officials denied any direct link to the confrontation with North Korea over its nuclear activities, which they said was being handled diplomatically.
The BBC Pentagon correspondent says the aim is to send a clear signal to North Korea not to take advantage of any conflict between Washington and Baghdad.
'Peaceful solution'
Tension between Washington and Pyongyang over North Korea's nuclear programme has been rising since October last year.
The United Nations' nuclear watchdog, the International Atomic Energy Agency (IAEA), is to meet on 12 February to consider asking the UN Security Council to act against North Korea.
"I've exhausted all possibilities within my power to bring North Korea into compliance," IAEA chief Mohamed ElBaradei said on Monday.
Also on Monday, White House spokesman Ari Fleischer said President George W Bush still believed the North Korean standoff could be resolved peacefully.
"That doesn't mean the United States won't have contingencies and make certain those contingencies are viable," Mr Fleischer told reporters.
Pentagon officials insist that no decisions have been made. But moves reportedly being considered include:
US Defence Secretary Donald Rumsfeld held talks on Monday in Washington with a visiting South Korean presidential envoy, Roh Moo-hyun.
A US spokesman said the 45-minute meeting had dealt with the future of US forces stationed in the South.
The envoy is also due to meet Secretary of State Colin Powell.
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