Charles Robert Jenkins, a former U.S. soldier who is alleged to have deserted his unit and defected to North Korea in 1965, must undergo a full investigation if he visits Japan to meet his wife, Hitomi Soga, a senior U.S. diplomat said Tuesday.

"We're not able to make any assurances before a full investigation would be made whenever the gentleman would present himself," James Kelly, assistant secretary of state for East Asian and Pacific affairs, told a news conference.

Kelly thus clarified the U.S. position on the issue: that Japan must hand Jenkins over to the U.S. before Washington can decide whether to meet Tokyo's request that he receive preferential treatment.

Jenkins could face a court-martial for desertion.