NEW YORK (BLOOMBERG) - As the US and Europe mount increasingly frantic efforts to deter Russia from any invasion of Ukraine, it's Chinese President Xi Jinping who may have the biggest influence on Mr Vladimir Putin's timetable.

The Russian President has said he will join Mr Xi at the opening ceremony on Feb 4 of the Beijing Winter Olympics, where the Chinese leader has lavished billions of dollars to showcase his nation's superpower status to the world.

The last thing Mr Xi needs is for Mr Putin to overshadow China's big moment by triggering a global security crisis with the US and Europe.

That's especially the case given Mr Xi is looking to bolster his prestige at home as he seeks endorsement for an unprecedented third term later this year.

The nations have often had each other's backs on the global stage. They've worked in concert to block United Nations Security Council resolutions critical of either, and aligned on collective issues like North Korea.

They revelled in the messy US withdrawal from Afghanistan. And they've largely stayed neutral on actions declared to be in the other's national interest - such as Russia's annexation of Crimea in 2014.

Mr Xi called Mr Putin an "old friend" when they chatted in mid December, while the Russian leader hailed what he said was a "responsible joint approach to solving urgent global issues".

But kicking off an invasion of Ukraine in the middle of Mr Xi's Olympic moment would throw a wrench into such warmth, and risk drawing China into the diplomatic fray.

It's possible Mr Xi asked Mr Putin in their recent call not to invade Ukraine during the Games, according to one diplomat in Beijing who asked not to be identified talking about such scenarios.

Mr Putin has repeatedly denied he currently intends to attack Ukraine.

China's Foreign Ministry underscored the importance Beijing attaches to the issue at a Jan 14 news briefing. All countries should observe a traditional UN Olympic Truce resolution "from seven days before the start of the Olympic Games until seven days after the end of the Paralympic Games", a spokesman said.

That's a window spanning from Jan 28 to March 20, when eastern Ukraine's frozen winter landscape begins to turn to cloying mud in spring thaws that military analysts in Moscow and the West believe would hinder a rapid Russian incursion.

The China-sponsored UN resolution was adopted by consensus last month, with Russia's representative urging all nations to observe the truce.

"Putin needs to take into account the interests of ideological partners and behave as carefully as possible," said Mr Andrei Kolesnikov, a senior fellow at the Carnegie Moscow Centre. "If Putin invades, he will create a very negative backdrop for the Olympic Games."

Russia is likely to wait at least until next week, when it says it will get a written responses from the US to its security demands.

After meeting on Friday in Geneva with Secretary of State Antony Blinken, Russian Foreign Minister Sergey Lavrov dismissed Western "hysteria" over Ukraine and repeated that Russia has no plans to invade its neighbour, even as it's massed some 100,000 troops near the border.

While Russia's less likely to launch a full-scale invasion immediately, it may opt for a more limited incursion into Ukraine around mid-February, two people familiar with recent Western assessments said.

Other actions including cyber attacks and attempts to destabilise Ukraine could take place in parallel or precede an intervention.

That assessment doesn't mean a larger invasion is out of the question, as Western allies have repeatedly said they don't know Mr Putin's intentions.

Russian forces continue to arrive in Belarus for joint military drills from Feb 10-20, amid US and Nato alarm that they could be used to attack Ukraine from the north. The closing ceremony at the Winter Olympics is on Feb 20.

Mr Putin and China have been here before. Russia's 2008 war with Georgia erupted on the day of the opening ceremony of the Beijing Summer Olympics, to the chagrin of Chinese leaders, prompting Mr Putin to fly home to direct military operations.

Days after Mr Putin hosted the closing ceremony of the 2014 Winter Olympics in Sochi, on which he'd spent a record US$50 billion (S$67.24 billion) to stage the Games, Russian forces began their operation to annex Crimea from Ukraine.

Mr Putin plans to brief Mr Xi on Russia's demand for security guarantees from the US and its North Atlantic Treaty Organisation allies when the two meet in Beijing, Kremlin spokesman Dmitry Peskov told reporters on Tuesday.

While there's been "no coordination" between them on the issue, "naturally, President Putin will inform Xi about what is going on", he said.

Asked at a briefing this week about the possibility of a Russian invasion, Foreign Ministry spokesman Zhao Lijian said Beijing advocates "balanced and just treatment of security concerns" while calling on all sides to "resolve differences through dialogue and consultation".

Russia has little incentive to antagonise China, its largest trading partner with total trade of US$112 billion in 2020 and a giant consumer of Russian energy and minerals.

China was the single biggest importer of Russian coal, buying more than 29 million tonnes in 2020 or 15 per cent of total exports, according to the RBC news site.

Amid the diplomatic efforts to defuse the current crisis, US President Joe Biden has issued increasingly urgent warnings about the risk of a Russian assault on Ukraine.

The US and Europe have threatened "severe" sanctions in response if that happens, measures that may cause Mr Putin to draw even closer to China to mitigate the impact on Russia's economy.

Still, some say if Mr Putin does plan to act, he will do so at the best time for Russia, despite the potential fallout.

"Putin can't sacrifice Russia's strategic interests and security to make a neighbour feel good, even if he is highly respected and strategically important," said Ms Tatiana Stanovaya, a political consultant and founder of R.Politik.

If the Russian leader believes security talks with the US are achieving nothing "then he will go into Ukraine, regardless of any request from China".