Chinese President Xi Jinping and Russian President Vladimir Putin are in the midst of a budding bromance.

The two strongmen celebrated Mr Putin's last birthday over vodka and Russian sausage and afterwards Mr Xi called the Russian President his best, most intimate friend.

With the two cosying up to Iran, many in the West are worried about a new "Axis of Autocrats" emerging.

The China-Russia relationship, of course, has been helped along by a common enemy: US President Donald Trump, who has recently slapped more sanctions on Russia and more tariffs on China.

President Trump has recently slapped more sanctions on Russia. ( AP: Pablo Martinez Monsivais )

Mr Putin and Mr Xi have met 26 times and will meet again later next month. Their nations are forging the deepest and strongest relationship since their last formal split in 1979 when Russia was the Soviet Union.

Their biggest ambition is to thwart American dominance in the world order and, with help from Iran, they are proving effective in shaping events from Syria to North Korea.

Senior Associate Professor Stephen Nagy from Tokyo's prestigious International Christian University has been carefully watching the geopolitical plates shift over the past decade and says the new Russia-China partnership is more a marriage of convenience.

"China is feeling the heat, so by strengthening relations with Russia, stressing comradeship between Xi Jinping and Vladimir Putin, the growing economic and military tie — this is a way to send a message to the United States that China does have options and Russia is a powerful option that can provide energy resources as well.

"It's also, importantly, an ideological partner that appreciates authoritarianism."

Xi Jinping and Vladimir Putin have met 26 times and will meet again in September. ( Reuters: Jason Lee )

But Professor Nagy said real ties were developing.

Last year two-way trade was up 20 per cent to more than $100 billion and, critically, Russia has become China's biggest and most secure supplier of crude oil.

"This is a real shift. Before we didn't have much of a trade relationship between the two states. This is an important indicator that both states see each other as important partners."

The most significant turnaround though is their military relationship. They now conduct joint military exercises from the Sea of Japan to the Mediterranean.

For decades, Russia resisted selling its most advanced military equipment to China but not anymore.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 27 seconds 27 s Vladimir Putin says Russia has tested an array of new strategic nuclear weapons.

"If we look back 15 years the Russians only provided second or third-grade military hardware to China but today Russia is providing top-grade military technology and equipment. This is indicative of a strategic shift on the Russian side," Professor Nagy said.

In the longer term Russia may have more to fear from a rising aggressive China, but for now, Professor Nagy said the two acting in unison was an effective way to confront the US without leading to direct conflict.

"We are not going to see China push back directly against the United States, but it will build capabilities and capacities with countries like Russia that can contribute to its social and economic stability and the ability of both to push back indirectly against the US."

Looking back at history, it seems unwise for the US to stimulate the formation of a powerful Chinese-Russian axis.

One reason the United States won the Cold War was it befriended China in 1972 and together they confronted the Soviet Union. The Soviet Union's downfall only took 20 years from there.

And the architect of that move, master political strategist Henry Kissinger, has apparently counselled Mr Trump to pursue "a reverse Nixon China strategy" by seeking to befriend Moscow to isolate Beijing.

It's an acknowledgement of how the Russia-China relationship can define the world order.