
One official, speaking on condition of anonymity, said planning had been underway for a trip in the near term but it was determined now was not the appropriate time.
The official said South Korea had been consulted regarding the change in travel plans.
Austin will leave office by Jan 20, when US President-elect Donald Trump is inaugurated.
Yoon’s declaration of martial law late on Tuesday sought to consolidate power, ban political activity and censor the media.
It sparked outrage on the streets and concern among South Korea’s international allies.
South Korea’s defence minister, who recommended the move, has resigned.