In this June 12, 2018 photo, DPRK leader Kim Jong Un, left, and US President Donald Trump shake hands at the conclusion of their meetings at the Capella resort on Sentosa Island in Singapore. (SUSAN WALSH / AP)

WASHINGTON - US President Donald Trump said on Monday that progress is being made on the issues related with the Democratic People's Republic of Korea (DPRK).

"Looking forward to my next summit with Chairman Kim!" US President Donald Trump tweeted, referring to DPRK's top leader Kim Jong-un

While posting a picture of him sitting behind a desk and reading a piece of paper, Trump tweeted, "Christmas Eve briefing with my team working on North Korea - Progress being made." The DPRK is also referred to as North Korea.

READ MORE: DPRK says it won't denuclearize unless US removes threat

"Looking forward to my next summit with Chairman Kim!" he said, referring to DPRK top leader Kim Jong-un.

The first-ever summit of Trump and Kim took place in Singapore in June, followed by a joint statement in which the United States agreed to provide security guarantee to the Asian nation in return of Pyongyang's commitment to denuclearization.

Earlier in the day, a US federal court judge ruled that the DPRK should pay over US$500 million for the death of a US citizen, Otto Warmbier, local media reported.

Chief Judge Beryl Howell of the US District Court for the District of Columbia has ruled that the DPRK should pay the money to Warmbier's parents, in a measure to hold the Asian nation accountable for the death of their son.

Warmbier's parents, Fred and Cindy Warmbier, have been seeking more than 1 billion dollars in damages from the DPRK in a lawsuit reportedly filed in April, saying the massive financial penalty would tell Pyongyang that it cannot take US citizens hostage.

However, the Fox News said that the ruling is largely symbolic since the DPRK is highly unlikely to accept or obey it.

Warmbier was an American university student who was arrested and sentenced to 15 years' imprisonment on suspicion of stealing a propaganda poster during a visit to the DPRK in 2016.

He was released in June 2017 and died six days after returning to the United States.

The DPRK said that Warmbier's death was a "mystery" as his health indicators and examination results were all normal when he left the country.

After Warmbier's death, the Trump administration relisted the DPRK as a state sponsor of terrorism in November 2017.

However, the relations between the DPRK and the United States have improved since earlier this year. The first-ever summit between Trump and  Kim was held in Singapore in June. In a joint statement released after the meeting, the United States agreed to provide security guarantee to the DPRK in return for Pyongyang's commitment to denuclearization.

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Although differences between the two sides remained over key issues like the scale of denuclearization, US sanctions, and whether to issue a war-ending declaration, momentum for talks continued.

Trump revealed on Dec 1 that his second meeting with Kim was likely to happen in January or February next year.