Conservative protesters hold portraits of U.S. journalists Euna Lee, left, and Laura Ling during an anti-North Korea rally last week demanding for the release of the journalists. (Jo Yong-Hak/Reuters)The United States said Monday that two American journalists convicted and sentenced to 12 years of hard labour in North Korea are innocent.

White House spokesman Robert Gibbs told reporters in Washington that the Obama administration considers the detention a humanitarian issue and is working to win the release of Laura Ling and Euna Lee.

The circumstances surrounding the trial of the two journalists from June 4 to 8 and their arrest for "grave crimes" three months ago on the China-North Korean border have been shrouded in secrecy, as is typical of the reclusive nation.

Earlier Monday, White House spokesman Bill Burton said President Barack Obama was "deeply concerned" about the plight of the women.

Not wanting to provoke the unpredictable regime that runs North Korea, the families of the two women have kept a low profile. Between tears, they struggle with anger, feeling helpless and occasionally hopeful.

Laura Ling's sister, Lisa Ling, has been one of the few family members to speak to the media.

"My sister is an amazing journalist and she's very passionate about what she does," she said. "Quite honestly, the story that my sister went to do wasn't one that we were that concerned about…because they had no intention when they left the United States to cross into North Korea."

Whether the two mistakenly wandered across a poorly marked border isn't known. They were reportedly digging into a story on the trafficking of North Korean women across that border for eventual sale, often as brides, inside China, according to Ling.

Their convictions come amid a tense standoff between North Korea and the West following Pyongyang's latest nuclear weapon test and a recent series of missile launches that have sparked the ire of the international community.

The sentence follows U.S. Secretary of State Hillary Clinton's warning on Sunday the United States was considering putting North Korea on its list of states that sponsor terrorism.

"The timing probably could not have been worse for these two journalists," the CBC's Michel Cormier reported from Beijing on Monday.

Judging by past incidents, North Korean officials may be trying to angle the U.S. into dropping demands for sanctions against Pyongyang in the UN Security Council, Cormier said.

'High-stakes poker game'

New Mexico Gov. Bill Richardson, a former U.S. ambassador to the UN who has negotiated with North Korea in the past, said Monday he had been contacted by the Obama administration for his thoughts on the case.

"This is a high-stakes poker game," he said in an interview Monday morning with NBC's Today show.

"In previous instances where I was involved in negotiating, you could not get this started until the legal process had ended."

The journalists — working for former vice-president Al Gore's California-based Current TV — were arrested March 17 as they were reporting about the trafficking of women. It's unclear if they strayed into the North or were grabbed by aggressive border guards who crossed into China.

Gore spokeswoman Kalee Kreider did not have an immediate response to the sentencing.

The women cannot appeal as they were tried in North Korea's highest court where decisions are final.

The sentences are much harsher than what many observers had hoped for. The trial was not open to the public or to foreign observers.

With files from The Associated Press