SEOUL, South Korea (AP) — North Korea on Thursday criticized organizers of the World Economic Forum in Davos for revoking an invitation to its delegation in the wake of a nuclear test.

The WEF sent an invitation to North Korea last autumn but withdrew it after Pyongyang defiantly conducted what it called a hydrogen bomb test last week.

There is widespread skepticism over whether the blast was truly an H-bomb test, but world powers are looking for ways to punish the North. The test, even if not a hydrogen bomb, will still likely push the country closer toward a fully functional nuclear arsenal.

North Korea's ambassador in Geneva wrote in a letter to the World Economic Forum that the decision to revoke the invitation was "based on unjust political motivation."

In the letter, obtained by The Associated Press, So Se Pyong writes that the WEF's move "constitutes an act of taking sides with certain forces that pursue extremely hostile policy against the DPRK." The acronym is commonly used for North Korea.

The letter is dated Jan. 14 and addressed to Philipp Roesler, a member of the WEF's board and formerly of the German government.

The WEF will hold its annual high-profile gathering of heads of state, CEOs and public figures next week in the Swiss ski resort of Davos. The forum is expected to draw more than 2,500 participants from more than 100 countries.

North Korea last attended the forum in 1998, according to South Korean media.

Masha Macpherson in Paris contributed to this report.