(CNN) The US may target Chinese companies as part of new North Korea sanctions, an administration official said this week , even as diplomats are working with Beijing at the UN to reach a new international agreement.

Thornton's testimony came as the House of Representatives was voting on a sweeping bill with new sanctions targeting Russia, Iran and North Korea

Her comments show the delicate balancing act US President Donald Trump's administration is walking on North Korea, where China is both a key ally for bringing pressure to bear on Pyongyang, but also a major potential target for sanctions designed to limit North Korean trade and imports.

Getting China on side

Washington has looked to China for progress on North Korea, even as Pyongyang ramped up missile and nuclear testing since Trump's election.

This month, North Korea claimed it had tested a nuclear capable intercontinental ballistic missile , after which US Secretary of State Rex Tillerson said "global action is required to stop a global threat."

Beijing -- as both North Korea's primary ally and a UN Security Council member -- is the most important player in any proposed global action.

But a perceived failure by Beijing within the US to halt such testing has caused relations with Washington to cool . Last month, Trump tweeted that he wished "we would have a little more help with respect to North Korea from China, but that doesn't seem to be working out."

"We strongly urge the US to immediately correct its wrongful actions to avoid affecting bilateral cooperation on relevant issues," said Chinese Foreign Ministry spokesman Lu Kang at the time.

Speaking to reporters Tuesday, the US ambassador to the UN Nikki Haley said progress was being made with China on new international sanctions targeting North Korea.

"We're constantly in touch with China ... things are moving but it's still too early to tell how far they'll move," she told reporters

"The true test will be what (the Chinese) have worked out with Russia (and whether) Russia comes and tries to pull out of that."

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Tong Zhao, an analyst at the Carnegie Tsinghua Center for Global Policy, said that while China has long been supportive of sanctions, confusion about the ultimate policies both countries are pursuing remains.

"The US strategy only makes sense to China if the ultimate US objective is to directly threaten the stability of the North Korean regime through a comprehensive economic embargo," he said.

"China has big concerns about that approach, but on the other hand US officials have also repeatedly said they are not trying to threaten the regime."

Apparent contradiction between statements and action causes confusion, Zhao said. He added the two countries "need to stop focusing on debating the specific tactics" and instead focus on overall strategy and goals with regard to North Korea.

Can sanctions succeed?

Even as Washington attempts to thread the needle on North Korean sanctions, some analysts argue they won't have much effect

"If Kim and his generals have to tighten their belts, the nuclear and missile programs are about the last things they will cut," John Delury, an expert at the Yonsei University Graduate School of International Studies in Seoul, wrote for CNN Opinion in December

"On the contrary, in the absence of diplomatic talks and under intensified pressure, Pyongyang is likely to double-down on its nuclear deterrent, which it sees as its best guarantee of national security and regime survival."

Thornton echoed Delury's comments Tuesday, even as she called for greater implementation of sanctions against North Korea.

"North Korea has no intention of abandoning its nuclear program in the current environment," she said. "North Korea will not give up its weapons in exchange for talks, even with economic concessions that provide sorely needed assistance to the North Korean people."

Washington, she added, would also not consider talks at this time, despite calls for just this from Beijing and Seoul . "We will not negotiate our way to talks," Thornton said.