“We’ve made very clear to them that that would cause a serious problem for us and in our relationship,” he added.

On Monday, Chinese foreign ministry spokesman Wang Wenbin accused Washington of “spreading false information”.

“It is the United States and not China that is endlessly shipping weapons to the battlefield,” Wang told a regular briefing.

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“We urge the United States to earnestly reflect on its own actions, and do more to alleviate the situation, promote peace and dialogue, and stop shifting blame and spreading false information.”

Blinken made similar comments in a series of interviews from Germany, where on Saturday he attended the Munich Security Conference and met with top Chinese diplomat Wang Yi.

There have been concerns China is deepening ties with Russia despite the conflict – but Wang insisted that Beijing was playing a constructive role, and would support dialogue and potential peace talks.

Appearing Sunday on ABC, Blinken emphasised that US President Joe Biden had warned China’s President Xi Jinping, as long ago as last March against sending weapons to Russia.

Since that time, “China has been careful not to cross that line, including by holding off on selling lethal weapons systems for use on the battlefield,” according to an administration source familiar with the issue.

A top US Republican senator who also attended the Munich conference, Lindsey Graham, said it would be a serious mistake for China to provide Russia with weapons.

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US warns China of ‘serious consequences’ if it supplies weapons to Russia for Ukraine war

US warns China of ‘serious consequences’ if it supplies weapons to Russia for Ukraine war

Doing so now, he said, would be “dumber than dirt. It would be like buying a ticket on the Titanic after you saw the movie”.

Graham, known as a well-informed foreign policy hawk, also said he had strong indications that the US will soon announce plans to train Ukrainian fighter pilots, which would represent a further step in the West’s gradually escalating efforts to arm Ukraine.

Graham said he believed the United States should declare Russia a state sponsor of terror for its actions in Ukraine – which would mean that China or any other country supplying it with arms would face sanctions.

Meanwhile, the EU’s foreign policy chief Josep Borrell said he told Wang that “for us, China supplying arms to Russia would be a red line in our relationship. He told me that they are not going to do it, that they don’t plan to do it. But we will remain vigilant.”

“I told him quite simply that that was unacceptable and can never happen again,” Blinken told CBS about the balloon incident.

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Wang on Saturday dismissed the US allegations of high-altitude spying in uncharacteristically strong language, calling them “hysterical and absurd”.

Blinken said that his counterpart had offered him “no apology”.

The tough-sounding exchanges came a day after US Vice -President Kamala Harris said in Munich that Russia had committed “crimes against humanity” in Ukraine through “widespread and systemic” attacks on the country’s civilian population.

Biden will speak in Warsaw on Tuesday to hail Nato’s unprecedented effort to help Ukrainians save their country as he marks the war’s first year.

On the same day, President Vladimir Putin is set to give his own speech in Moscow, three days from the February 24 anniversary of Russian tanks rolling into Ukraine.