By Lee Min-hyung

Kim Song, North Korean ambassador to the United Nations

North Korean Ambassador to the United Nations Kim Song plans to raise his voice against Washington's recent seizure of a North Korean cargo ship by holding a press conference at the U.N. headquarters, Tuesday (local time in New York).

This is in line with Kim's recent letter sent to U.N. Secretary-General Antonio Guterres. The letter was written to express the North's regret over the U.S.' decision to seize the 17,000-ton North Korean freight vessel.

Earlier this month, Washington detained the North's second-largest vessel, called Wise Honest, for allegedly violating U.N. Security Council resolutions by illicitly shipping coal from the North.

"We are, obviously, studying the letter ― it relates to the issue of sanctions on the Democratic People's Republic of Korea (the North's official name) and actions taken on the implementation of those sanctions," U.N. spokesperson Stephane Dujarric said Monday.

Expectations are that Kim will ramp up criticism of the U.S. for engaging in what Pyongyang called "illegal robbery" during the press conference.

According to the North's propaganda outlet the Korean Central News Agency (KCNA), the North said in the letter that the U.S. conducted the illicit act of robbery by taking the Wise Honest to American Samoa, which the North claimed was a violation of international law.

The KCNA also urged the U.N. to make a fair decision at a time when concerns are growing over the future of the Korean Peninsula after Washington's "gangster-like behavior."

"We are going to keep a close watch on the upcoming behaviors from the U.N.," the KCNA said.