SEOUL - North Korea accused the United States of robbery Tuesday and demanded the immediate return of a cargo ship seized for allegedly violating international sanctions.

In a statement in the official Korean Central News Agency, North Koreas foreign ministry warned of unspecified consequences in response to the U.S. seizure of the vessel.

The U.S. should carefully deliberate what consequences will follow in the current situation derived by their robbery and promptly return our ship, the Tuesday statement read.

The KCNA statement claimed the seizure violates the 2018 agreement between U.S. President Donald Trump and North Korean leader Kim Jong Un to improve bilateral relations.

The United States announced last week it had seized the Wise Honest, which was originally detained in April 2018 by Indonesian authorities.

The 17,000-ton vessel, North Koreas second-largest cargo ship, had been used to export North Korean coal in violation of international sanctions, U.S. officials say.

It is the first time that U.S. officials seized a North Korean vessel.

The move further strained ties between North Korea and the United States, which appear to be re-entering a period of hostility after a year of nuclear talks.

In recent weeks, North Korea has resumed testing ballistic missiles after refraining from such launches for a year-and-a-half.

U.S. officials have shrugged off the three short-range missile tests, saying the door remains open for talks with the North.

At their first summit in June 2018, Trump and Kim vowed to improve relations and to work toward the denuclearization of the Korean peninsula.

The talks broke down when a second Trump-Kim summit in Vietnam in February failed to result in a deal.

At that summit, Kim offered to dismantle a key North Korean nuclear site in exchange for the United States easing sanctions that are hurting the Norths economy.

Trump insisted he would not ease sanctions until North Korea agrees to abandon its entire nuclear weapons program.

The seizure of the Wise Honest is part of what U.S. officials have described as a campaign of maximum pressure against the North.

Under a series of U.S. and United Nations sanctions, North Korea is prohibited from a broad range of economic activities, including exports of materials such as coal.

North Korea has evaded the sanctions, in part by using dozens of ships such as the Wise Honest to conduct ship-to-ship transfers of raw materials.

When it was detained in 2018, the Wise Honest was carrying about 25,500 tons of coal -- a load valued at around $3 million at the time.

U.S. officials believe North Korea uses the money from coal sales to fund its weapons program.

The ship arrived this week at the port of Pago Pago in the U.S. territory of American Samoa.