Former US President Jimmy Carter is visiting North Korea in an effort to negotiate the release of a US man jailed there, Aijalon Mahli Gomes.
On his arrival in Pyongyang, Mr Carter met senior officials including North Korean deputy leader Kim Yong-nam.
Mr Gomes, 31, was sentenced to eight years' hard labour in April, after being found guilty of illegally entering the country from China.
US officials have called Mr Carter's visit a "private humanitarian trip".
"Obviously it's a mission to secure the release of Mr Gomes, but we don't want to jeopardise the prospect for Mr Gomes to be returned home by discussing any of the details," state department spokesman Mark Toner said.
Mr Carter was met at the airport by North Korea's nuclear negotiator, Kim Kye-gwan, North Korea's state news agency KCNA said.
Later he held "cordial" talks with the country's deputy leader, the agency said.
He is expected to spend one night in the communist country.
Mr Gomes, who had been teaching English in South Korea, reportedly crossed into North Korea in January. A devout Christian, he is thought to have gone there on a one-man peace mission.
He was visited by a US official and two doctors in a hospital in Pyongyang earlier this month. North Korea said in July that Mr Gomes had tried to commit suicide.
In visiting North Korea, Mr Carter is following in the footsteps of another former US President, Bill Clinton, who last year secured the release of two US journalists detained in North Korea for crossing the border.
The journalists, Laura Ling and Euna Lee, were pardoned and returned to the US with Mr Clinton.
Mr Carter's visit comes at a time of heightened tension between North Korea and the outside world, in the wake of the sinking of a South Korean warship.
International investigators say a North Korean torpedo sank the Cheonan, which went down near the disputed inter-Korean border on 26 March with the loss of 46 sailors.
Since then, the US and South Korea have embarked on a series of joint military exercises - sparking an angry response from Pyongyang.
Six-nation talks aimed at ending North Korea's nuclear ambitions have also been stalled for several months.