Lee, a Korean-American, and Ling, a Chinese-American, were detained close to the Tumen River which forms part of the border between China and North Korea, on March 17.
The reporters were filming a story about North Korean refugees for California-based Current TV, an online boradcaster set up by Al Gore, the former US vice-president.
There is speculation that the two reporters could be used as bargaining chips in the North's frayed relations with the US.
|Laura Ling, left, and Euna Lee were detained by North Korean border guards in March [AP]
North Korea state media has previously said the journalists would go on trial for "hostile acts" and for illegally entering the country, adding that the trial would be held "on the basis of the confirmed crimes committed by them".
Park Jeong-woo, a law professor at South Korea's Kookmin University and an expert on the North's legal system, told the Reuters news agency that according to North Korean law, "a person convicted of highly hostile acts can be subject to forced labour for a period of 10 years or more".
Human rights groups say conditions in North Korea jails are brutal, with torture commonplace and prisoners often dying from malnutrition and abuse.
Very little has been heard of the journalists since their arrest, but they were seen last month by the Swedish ambassador to North Korea, on behalf of the US, which has no diplomatic ties with the North.
"When I first got here, I cried so much. Now, I cry less," Ling was quoted as saying in a letter sent to her sister on May 15.
The families of the two women have appealed for their release.
"We aren't certain of the details of what happened on March 17, but we can say with absolute certainty that when the girls left US soil, they never intended to set foot onto North Korean territory," they said in a statement.
|Rallies were held across the US on Wednesday in support of the journalists [AFP]
On Wednesday friends and supporters of the two journalists held rallies and candle-lit vigils in several US cities calling for their release and appealing for leniency from North Korea.
"I wish this were all a bad dream," Ling's sister, Lisa, said in a letter read out in Washington's Freedom Plaza.
"We have a golden opportunity for a fresh start between our two countries," she said.
"Instead of trying to get reacquainted with one another through missile launches, nuclear tests and terse rhetoric, why not get to know each other over these two amazing girls who just wanted to tell a story?"
The last case of a US citizen arrested for crossing into North Korea was in 1996.
Evan Hunziker was held for three months on charges of spying.
Bill Richardson, a former official in the Clinton administration and now governor of the state of New Mexico, went to the North to secure his release and settle a $5,000 "hotel bill" imposed by the government to cover the cost of detention.