WASHINGTON  President Obama and his top national security aides on Monday urged North Korea to release “on humanitarian grounds” two American journalists sentenced to 12 years of hard labor for entering North Korean territory. But administration officials said that the harsh sentences were likely to be used as a negotiating ploy by the North as it tries to avoid new sanctions in response to its nuclear test two weeks ago.

In public statements, administration officials frequently referred to the two journalists as “young women” who might have inadvertently crossed the North Korean border, and urged North Korea to return them to their families. “Their detainment is not something that we’ve linked to other issues, and we hope the North Koreans don’t do that, either,” Robert Gibbs, Mr. Obama’s press secretary, told reporters on Monday afternoon.

Clearly, the sentencing on Monday of Laura Ling, 32, and Euna Lee, 36, to serve in North Korea’s famously brutal labor camps  where stories of starvation, overwork and mistreatment are legion  greatly complicated the Obama administration’s agenda. The administration has been working at the United Nations Security Council for a series of new sanctions that would both cut off funds to North Korea and interdict cargo, to search for missiles, weapons or nuclear technology.

Administration officials appeared to be weighing whether to send a special envoy in a high-profile effort to seek the release of the two women, who were detained by North Korean soldiers at the Chinese border on March 17. The two most likely candidates are former Vice President Al Gore, whose Current TV channel employs the two journalists, and Gov. Bill Richardson of New Mexico, who has visited North Korea a number of times and arranged the release of another American 15 years ago.