WASHINGTON - US President Donald Trump on Friday announced what he called the "heaviest sanctions" on the Democratic People's Republic of Korea (DPRK), a move that came amid signs of a growing rapprochement on the Korean Peninsula.

"We imposed today the heaviest sanctions ever imposed on a country before," Trump said in an address to a conservative activist group in the state of Maryland.

The new sanctions, the "largest-ever" package on the DPRK, will target 56 vessels, shipping companies, and trade businesses, said senior Trump administration officials at a background briefing earlier in the day.

The penalty, which is part of the US campaign of "maximum pressure" on Pyongyang, will designate 27 companies, 28 ships and one person, according to a statement released by the US Department of Treasury.

The Trump administration has engaged in "maximum pressure" against the DPRK since assuming office in early 2017 to curb Pyongyang's nuclear and missile development program.

US Treasury Secretary Seven Mnuchin pledged on Friday that Washington will impose more punishment on Pyongyang.

"We will continue as we see things that should be sanctioned, I can assure you, we will continue to roll out new sanctions," Mnuchin said at a White House briefing.

Mnuchin also noted that the United States has already slapped more than 450 sanctions against the DPRK, with about half of them launched in 2017.

The economic impact on the DPRK is unclear. It was not clear how the United States could enforce the new measures.

In his speech, Trump said that "hopefully something positive can happen" from the new sanctions measures.

Washington's latest move, however, came as Pyongyang and Seoul have embarked on an apparent rapprochement with the Pyeongchang Winter Olympics used as an opportunity over the past month.

US Vice-President Mike Pence signaled these sanctions earlier this month, threatening to slap the "toughest and most aggressive" sanctions on the already weakened DPRK.

Some experts believed his harsh rhetoric before he visited the games in Pyeongchang as the main reason that led the DPRK to call off a scheduled Feb 10 meeting with Pence during the games.

The DPRK sent its athletes and cheerleaders as well as a high-ranking delegation to Pyeongchang, showing its willingness to improve inter-Korean relations and ease tensions on the Korean Peninsula.

Kim Yo-jong, the younger sister of DPRK top leader Kim Jong-un, also delivered a letter of Kim Jong-un to South Korean President Moon Jae-in, inviting him to visit Pyongyang at a convenient time.

The timing of Trump's sanctions announcement is also noteworthy, coming hours after Moon said it would be significant for Seoul and Washington to closely cooperate to enable the inter-Korean talks and the denuclearization talks to make progress together.

In hosting Trump's daughter Ivanka, Moon noted that the joint efforts by Seoul and Washington to denuclearize the DPRK have failed for the past 25 years, saying the two countries must take the opportunity of the current dialogue mood.

Washington has hinted earlier about possible talks with Pyongyang, while showing no sign of easing the economic pressure.

"The maximum pressure campaign is going to continue and intensify. But if you (the DPRK) want to talk, we'll talk," Pence told a US reporter on his way back from Pyeongchang.

Apart from the new US sanctions, looming US-South Korean annual military drills have been seen as a threat that may dampen the recently generated positive momentum.

"We have to wait and see what the exercises look like. Some exercises can be very provocative and offensive," Douglas Paal, vice president for studies at the Carnegie Endowment for International Peace, told Xinhua in a recent interview.