In a rare news conference in New York, held by North Korea’s United Nations Ambassador Kim Song reiterated the demand Tuesday for the immediate return of his country’s cargo ship that was seized by the United States earlier in May.

"The United States should deliberate and think over the consequences its outrageous act might have on the future developments. Also the United States must return our cargo ship without delay," Kim said. "We regard it as part of our territory where our sovereignty is fully exercised."

He added that following the seizure, Pyongyang was closely monitoring Washington's "every move" including the intention to apply pressure on North Korea, forcing it to “kneel down.” The seizure of the ship was described by the ambassador as an "outright denial of the underlying spirit" of the first summit between President Donald Trump and North Korean leader Kim Jong Un, held last year in Singapore, in which both the nations “committed to establishing new bilateral relations."

Song accused the U.S. of violating the 2004 U.N. Convention on Jurisdictional Immunities of States and Their Property (which protects the "immunity of a State and its property from the jurisdiction of the courts of another State") and other international laws by seizing the ship, adding that he had written a letter to U.N. Secretary-General António Guterres, urging him to take “urgent measure” to ensure the immediate return of the vessel to North Korea.

U.N. spokesman Stéphane Dujarric confirmed Tuesday that Song’s letter had been received. "We're taking a look at it. The issue of sanctions, the implementation of sanctions, the interpretation of sanctions, is really a matter for the UN Security Council to decide and to discuss," he said, Turkish news outlet TRT World reported. 

The Department of Justice announced May 9 that the North Korean vessel, named “Wise Honest,” was being impounded to American Samoa, after being accused of illicit coal shipments in violation of sanctions imposed against the country. The 17,061-ton vessel, which was initially detained by Indonesia in April 2018, was reportedly one of North Korea’s largest bulk carriers used to deliver heavy machinery to the country.

The announcement came hours after reports of North Korea test-firing two short-range missiles. Following the missile test, POTUS told reporters at the White House his administration was keeping a close eye on North Korea, adding that while Pyongyang wanted to negotiate a deal, he was not sure whether it was ready for an agreement.

“We’re looking at it very seriously right now. They were smaller missiles, they were short-range missiles,” Trump said. “Nobody’s happy about it but we’re taking a good look and we’ll see. The relationship continues ... I know they want to negotiate, they’re talking about negotiating. But I don’t think they’re ready to negotiate.”

After the second summit between the two countries in Hanoi, Vietnam, was cut short in February, Washington claimed the North Korean leader had insisted on the complete removal of all sanctions on his country, which the U.S. did not agree to. Meanwhile, Pyongyang rejected the reasoning, stressing it had only asked for a partial lifting of the restrictions.