The two undisclosed 2012 trips by administration officials were aimed at seeing if a new level of cooperation could be forged with Kim Jong Un, who assumed power in late 2011.
Ranking officials refused to comment on the trips, although Korea experts in the United States said they were worth the effort despite the apparent lack of success.
"I don't know why at this point the administration just doesn't set the record straight on this," said a former U.S. official. "All it shows is that we were trying to walk the last mile with North Korea."
Sources told the Times the trips were aimed at personally encouraging the new leadership in Pyongyang to shelve its missile testing and tone down its overall belligerence; however, the North Koreans were not to be dissuaded.
The Times said the White House refused to comment on the election year missions in part because they did not want to open them up to scrutiny from Congress as well as the leadership in South Korea and Japan.
The missions appeared to be led by career diplomats and intelligence officials and apparently did not include any political figures or advisers from the administration.
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