North Korea on Saturday blamed Washington for the cancellation of a visit by a special American envoy to Pyongyang, citing joint US-South Korea military drills described as the "most blatant nuclear blackmail".

On Friday, the US State Department said North Korea had cancelled the invitation to an envoy who was to have sought the release of an American citizen held prisoner in the reclusive state.

News of the planned trip by US diplomat Robert King had raised hopes that Kenneth Bae, a 44-year-old American who has been prisoner in North Korea since November, might be released.

King had been due to fly to Pyongyang on Friday, but the State Department said the visit had been cancelled after North Korea rescinded its invitation.

"We are surprised and disappointed by North Korea's decision," a spokesman said at the time.

However North Korea on Saturday placed the blame for the cancelled visit at the feet of Washington, saying the US should have expected the move.

"We intended to allow the visit of the special envoy ... and have a sincere discussion with him," a foreign ministry spokesman said in a statement to the official Korean Central News Agency.

But joint military drills by the US and South Korea -- including "such grave military provocation as infiltrating B-52H strategic bombers into the sky above the Korean Pensinsula" -- had "beclouded the atmosphere", according to the spokesman.

The annual 10-day Ulchi Freedom Guardian joint exercise, which ended on Friday, is habitually condemned by Pyongyang.

The exercise is a practice response to a simulated North Korean invasion. Although largely played out on computers, it still involves more than 80,000 South Korean and US troops.

North Korea's response to the drill had been unusually muted up until Saturday, when the spokesman told KCNA the drills were "the most blatant nuclear blackmail against us".

As such, it was "surprising" that the US was caught off guard by the decision to cancel the envoy's visit, the spokesman said, according to KCNA.

Bae, a Korean-American tour operator whose Korean name is Pae Jun-Ho, was arrested in November 2012 as he entered the hardline communist state's northeastern port city of Rason.

North Korea, which strictly bans religious proselytizing, said Bae was a Christian evangelist who brought in "inflammatory" material.

He was sentenced to 15 years hard labor on charges that he was trying to topple the regime of young leader Kim Jong-Un.

His family and US officials say he is now very sick, and have called for his release as a humanitarian gesture.

Bae was tried at a time of high tension between the United States and North Korea over the reclusive nation's nuclear program,

The North has staunchly denied that the hefty jail sentence was crafted as a diplomatic bargaining chip, and indicated that it wanted policy changes, not diplomacy, from Washington to secure Bae's freedom.

North Korea has in the past freed detained Americans after visits from high-level emissaries such as former presidents Bill Clinton and Jimmy Carter.

In the heat of a crisis over the communist state's weapons programmes earlier this year, North Korea carried out its third nuclear test and threatened to strike the United States, but tensions have since eased.

America has been cool to North Korean overtures to restart talks, saying it is only interested in sitting down if Pyongyang commits to giving up its atomic weapons.

But releasing Bae, something the United States has been seeking for months, could help foster goodwill between the rival nations.