Citing sources familiar with the conversation, the newspaper reported that Armitage recently told national security adviser Condoleezza Rice that he and Powell would leave on 21 January 2005, the day after the next presidential inauguration.
According to the newspaper, Powell has indicated to associates that he would be leaving for personal reasons rather than any differences over the administration's foreign policy.
The report said Powell indicated that a commitment made to his wife was a key factor in his desire to limit his tenure to one presidential term. There are 18 months left in Bush's current term.
Powell doctrine swept aside
The current administration has been characterised by fierce policy debates often between Powell and more hawkish members, the newspaper said.
The administration's policy of pre-emptive action against foreign nations and its interventions in both Afghanistan and Iraq fly in the face of of the secretary of state's famous "Powell Doctrine" on military strategy, that he outlined at the end of the 1991 Gulf War.
At that time, Powell argued that military action should be used only as a last resort and only if there is a clear risk to national security by the intended target. He also said there must be strong support for the campaign by the general public, and that there must be a clear exit strategy from the conflict in which the military is engaged.
Contenders for the job
A State Department spokeswoman declined comment on the report.
Rice and Deputy Defence Secretary Paul Wolfowitz are the leading candidates to replace Powell, The Post reported, citing sources inside and outside the administration.
Rice appears to have an edge because of her closeness to the president, the newspaper said.
It cited sources as saying that because Wolfowitz is considered more of a strategic thinker than a manager, he could be tapped as national security adviser if Rice became secretary of state or entered politics.