“If China won’t act, we will,” US Secretary of State Antony Blinken said after meeting Chinese President Xi Jinping on Friday.

For it’s part, China has warned the US not to cross its “red lines,” including Taiwan which Beijing claims as its own.

Mr Blinken said he did not raise the issue of Chinese app TikTok with President Xi, the future of which is looking precarious in the US where it could be closed down if it’s not sold.

Despite the tetchy comments, the counterparts stressed relations had advanced in a number of areas.

China’s ‘red lines’

Mr Blinken, in China for the second time in less than a year, pointed to improvements in the relationship but urged greater action from Beijing on areas including curbing support for Russia.

Meeting Mr Blinken in Beijing’s Great Hall of the People, Mr Xi said the two countries had “made some positive progress” since he met with US President Joe Biden in November.

“The two countries should be partners, not rivals,” Mr Xi said. But he issued a warning over what China considers US pressure to curb its economy, which have included a sweeping ban on semiconductor exports and TikTok.

“We hope the US can also take a positive view of China’s development,” Mr Xi said. “When this fundamental problem is solved,” he said, “relations can truly stabilise, get better and move forward”.

Earlier China’s Foreign Minister Wang Yi warned Blinken that US pressure could trigger a “downward spiral”.

Mr Wang also warned that the question of self-ruled Taiwan was the “first red line” that must not be crossed in China-US relations.

Taiwan used to be part of China but has been self ruled since 1949 when communist forces declared the People’s Republic on the mainland. The democratic island nation has never been ruled by Communist China.

Pressure on Russia

Mr Blinken described his talks with Mr Wang at the Diaoyutai state guesthouse — which lasted more than five and a half hours — “extensive and constructive”.

He announced that the two countries will in the coming weeks hold their first formal talks on managing artificial intelligence, a rising area of concern as the technology progresses rapidly.

But Mr Blinken sounded a warning on China’s support for Russia’s “brutal war of aggression” in Ukraine, saying that Beijing — while stopping short of direct arms exports — has helped Russia ramp up production of rockets, drones and tanks.

Russian President Vladimir Putin said this week he will visit China in May.

“Russia would struggle to sustain its assault on Ukraine without China’s support,” Mr Blinken said.

‘If China won’t act, we will’

Talking to UK broadcaster the BBC afterwards he said Washington could take unspecified actions, which could mean sanctions, against Beijing.

“We’ve taken action already against Chinese entities that are engaged in this,” he said.

“And what I make clear today is that if China won’t act, we will.”

But he said China has been helpful in the past, including in discouraging nuclear weapons use by Russia, and said that Mr Wang promised to stay in touch on the Middle East, a key priority for Washington.

Pointing to China’s ties with Iran, whose shadow war with Israel has come into the open, Mr Blinken said: “I think the relationships that China has can be positive in trying to calm tensions, to prevent escalation, avoid the spread of the conflict”.

Addressing gaps ‘responsibly’

US officials and experts believe that Mr Xi’s foremost priority is to manage headwinds in the Chinese economy and that, at least in the short term, he is looking to avoid flare-ups with the West.

As he opened the meeting with Mr Wang, Mr Blinken said China and the US should manage the relationship “responsibly” and added: “I hope we make some progress on the issues our presidents agreed” on at the California summit.

The two countries should be as “clear as possible about the areas where we have differences — at the very least to avoid misunderstandings, to avoid miscalculations,” Mr Blinken said.

“That really is a shared responsibility that we have not only for our own people, but for people around the world, given the impact that our relationship has,” he said.

Mr Biden, who recently spoke by telephone with Mr Xi, faces a tough re-election fight in November against his predecessor Donald Trump, who has cast China as an enemy and vowed a hard line.

The Biden administration has pointed to wins with China, with Mr Blinken highlighting efforts by China to curb precursor chemicals to fentanyl, the painkiller behind an epidemic in the United States.

He said he urged China to carry out further prosecutions.

But while open to co-operation, Mr Biden has increased pressure on China beyond Mr Trump in some areas.

In the latest move, the US Congress, with Mr Biden’s support, voted to force the divestment of TikTok from Chinese company ByteDance or risk a ban in the United States.

Mr Blinken said, however, that TikTok did not come up in his talks.

US officials allege security and privacy concerns over the app, which has taken off among US teenagers.

ByteDance denies the allegations and has insisted it has no intention of selling the app.