The last-minute decision to postpone the 10-day trip that would also include a visit to Vietnam came after Hagel faced criticism over his performance from unnamed officials inside President Barack Obama's administration in a series of news reports.

The trip had yet to be publicly announced when officials gave word the visit would be postponed, likely until next year.

Some of the reports suggested Hagel and other officials might be replaced in a shake-up of Obama's national security team after the midterm elections held on 4th November.

Officials have dismissed the speculation and the criticism, saying the trip was put off because Hagel needed to attend a Congressional hearing.

"It was deemed the most prudent thing to do to make sure he was available to answer questions from Congress about any number of matters that are on their minds," Pentagon spokesman Rear Admiral John Kirby told a news conference.

"This was simply a prudent scheduling decision and nothing more," Kirby said.

The move to delay the visit was unusual, especially so close to a planned trip.

In the past, Hagel has gone ahead with scheduled tours to Asia even at politically-charged moments.

Last year, Hagel flew to Southeast Asia as the Obama administration appeared poised to take military action against the Syrian regime.

Kirby said postponed trip should not call into question the Pentagon chief's commitment to the administration's strategic "rebalance" to the Asia-Pacific region.

Hagel has taken more than six trips to the Pacific region during his tenure and remains heavily focused on Asia, he said.