North Korea will put a detained US citizen on trial on September 14, state media says, less than a week since Matthew Miller made a highly unusual televised plea for help from Washington.

Miller, one of three Americans being held in North Korea, was arrested in April after he apparently ripped up his visa at immigration and demanded asylum.

“The Supreme Court of the Democratic People’s Republic of Korea (North Korea) decided to judge American Miller Matthew Todd, now in custody, on September 14, according to the indictment of a relevant institution,” the official news agency KCNA said.

The statement offered no further details.

North Korea said in July it would put him and another detained US citizen, Jeffrey Fowle, on trial on unspecified charges related to “perpetrating hostile acts.”

On September 2, Miller – along with Fowle and a third US citizen being held in North Korea, Kenneth Bae – pleaded for their freedom as Pyongyang minders looked on in an interview with CNN.

They urged Washington to send an envoy to the isolated authoritarian state to negotiate their release.

“My situation is very urgent,” Miller said during the interview.

“I think this interview is my final chance to push the American government into helping me,” he added, wearing a dark turtleneck and often looking away from the interviewer.

US officials vowed the day after the interviews were aired that they would “leave no stone unturned” in their efforts to free the three men.

But State Department spokeswoman Jen Psaki refused to outline US efforts publicly, saying Washington did not want to jeopardise any diplomacy.

She would not discuss whether Washington was prepared to send a high-level envoy to Pyongyang as it has in past cases, when former president Bill Clinton and ex-governor Bill Richardson successfully won the release of detained Americans.

Fowle entered the North on April 29 and was detained after reportedly leaving a Bible at a hotel.

Bae was arrested in November 2012 and later sentenced to 15 years of hard labour on charges of seeking to topple the North Korean government.