CNN)The Trump administration on Thursday issued its first set of sanctions aimed at North Korea since the failed summit last month between Kim Jong Un and President Donald Trump, going after two Chinese shipping companies that have helped Pyongyang evade restrictions imposed by the US and United Nations Security Council.

A senior administration official told CNN that this action should not be seen as a sign the US is ramping up economic pressure on North Korea but as part of the continuous push to ensure that entities and countries are not taking their foot off the gas pedal.

“It is really meant to be a continuous activity of the US, and it really needs to a continuous activity of … all of the UN members to maintain the integrity of the sanctions,” the official said.

In Hanoi, the North Koreans wanted the majority of sanctions lifted in return for some action on denuclearization. It was their aggressive demand for substantial sanctions relief, coupled with unclear commitments on denuclearization, that sank any possible deal.

With these new sanctions, the Trump administration is reiterating that it will not cede to North Korea’s demands. Instead, it is reminding companies like the Chinese ones targeted Thursday that they will not get away with any illicit activity with Pyongyang.

“We will find out, and they are at risk,” the official said, threatening other companies — either shipping or financial — that any illicit activity with North Korea could result in sanctions.

Trump’s national security adviser, John Bolton, echoed that sentiment on Twitter.

“Everyone should take notice and review their own activities to ensure they are not involved in North Korea’s sanctions evasion,” Bolton wrote, particularly calling out the maritime industry as needing to do more to clamp down on the illicit activity.

Members of Congress have encouraged the US to slap more sanctions on North Korea in recent weeks. They note that the sanctions regime on the country has substantially slowed in the last year. The Trump administration has sanctioned 182 persons or entities for North Korean violations since March 2017 but only 26 since February of 2018, according to research from the Foundation for Defense of Democracies.

Members of Congress also worry that the US is not putting enough resources toward enforcing the sanctions that are already in place, according to a senior aide on Capitol Hill.

For now, the administration believes the sanctions are working, and that more effective enforcement will have to come from influential countries, like China.

“It is really a matter of international will, more than a question of resources,” the official said, noting there has been “leakage,” specifically from China. The official noted that the sanctions are working given that North Korean imports and exports are both down.

Despite the Trump administration being in the midst of trade negotiations with China, Bolton also pointed a finger directly at Beijing when he discussed the new sanctions on Thursday.

“China could really hold the key to this here if they press North Korea hard enough,” Bolton said during an interview with Breitbart on Thursday. “China is obviously North Korea’s dominant trading partner. Over 90% (of) North Korea’s external trade is with China. We continue to press China to enforce all the sanctions against North Korea.”

The move comes as diplomacy has once again hit a standstill, despite an administration official’s insistence that “the door is wide open for continued discussions with North Korea.”

Since the Hanoi summit almost a month ago, no working-level meetings between the US and North Korea have been publicly announced. While the White House and the State Department maintain that the door is open on the US side, Secretary of State Mike Pompeo has made it clear that he is done chasing Pyongyang, given the disproportionate amount of outreach that came from the US side last year.