The statement on the official Korean Central News Agency (KCNA) triggered immediate concerns in the United States, which said there were concerns over his "health and welfare".
The news comes as the US pushes North Korea to end its year-long boycott of six-nation nuclear disarmament talks.
Call for access
The US state department did not confirm the man's identity, but said there was "great concern about the lack of transparency" in the handling of the case.
"Our primary concern is, obviously, we want our US citizen back"
US state department spokesman
"We continue to press for appropriate consular access, full rights under North Korean law," PJ Crowley, a department spokesman, told AFP.
He said the US will continue to monitor the situation through the Swedish embassy in Pyongyang "to make sure that he has appropriate representation should North Korea follow through with any legal proceeding".
"Our primary concern is, obviously, we want our US citizen back," added Crowley.
Last week US officials said a Swedish diplomat in Pyongyang had been allowed to see Gomes for the first time.
The US and North Korea do not have diplomatic relations and the Swedish embassy represents Washington's interests in Pyongyang.
Despite the announcement of the trial, the news has raised speculation that North may be preparing to expel Gomes as a goodwill gesture.
"I believe North Korea intends to expel him after completing legal procedures," said Kim Yong-Hyun, a North Korea expert at Seoul's Dongguk University.
"I guess North Korea has no intention to cause any serious trouble over this case amid ongoing diplomatic efforts to resume six-party talks."
North Korea is pressing the US to agree to talks on a permanent peace pact to replace the armistice that ended the 1950-53 Korean War.
It is also seeking US commitment to discuss a peace pact and a lifting of UN sanctions before it returns to six-nation nuclear disarmament talks.
In the past North Korea has used detained US citizens as bargaining chips, typically releasing them a few months after their capture.
In February North Korea freed a US religious activist it had held since December.
Robert Park, a US citizen of Korean descent, admitted to illegally entering the country to raise awareness about human rights abuses.
In March last year, the North convicted two female US television reporters for illegal entry and sentenced them to 12 years of hard labour.
They were later pardoned and released after a few months in captivity when Bill Clinton, the former US president, flew to Pyongyang and met Kim Jong-il, the North Korean leader, to secure their freedom.