The US has imposed sanctions on two Chinese companies that have helped North Korea evade restrictions imposed by Washington and the UN Security Council, a senior administration official said.

The official told CNN on Thursday 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.

During the second summit between President Donald Trump and Pyongyang’s Kim Jong-un last month 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, there was no outcome from the summit.

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 on 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 on Thursday.

“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.

The Trump administration has sanctioned 182 persons or entities for North Korean violations since March 2017 but only 26 since February of 2018.