Chinese President Xi Jinping and visiting Russian President Vladimir Putin on Friday opposed further expansion of the North Atlantic Treaty Organization, with fears mounting about Moscow's possible invasion of Ukraine.

In a joint statement released by Russia, Xi and Putin, who met in Beijing before attending Friday's opening ceremony of the Winter Olympics, also lambasted a security partnership among Australia, Britain and the United States called AUKUS.

Russian President Vladimir Putin (L) and Chinese President Xi Jinping meet in Beijing on Feb. 4, 2022. (Kremlin Press Office/Handout/Anadolu Agency/Getty/Kyodo)

During their face-to-face talks, the two leaders confirmed the solid unity between China and Russia, state-run media reported, as their tensions with the United States and its allies have been escalating over several issues including Ukraine.

Putin has demanded that NATO pull back troops and weapons from Eastern Europe, while Xi has opposed the politicization of sports as the United States and some democratic countries have staged a "diplomatic boycott" of the Beijing Olympics.

Xi has not visited other nations since early 2020, when the coronavirus started to rage. He is expected to resume face-to-face meetings with his counterparts in a full-fledged manner in the wake of the Olympics to boost China's clout in the global arena.

On Friday, Xi told Putin that he stands ready to work with the Russian president to chart the future and provide guidance for bilateral relations under new historical circumstances, the official Xinhua News Agency reported.

Xi added he is willing to work with Putin to help transform high-level mutual trust between the two countries into cooperation in all fields that produce results, according to Xinhua.

Chinese and Russian media reported Putin told Xi that the two countries have continued to develop their ties under a friendly and strategic partnership, expressing hope that they will further bolster cooperation in the international community.

U.S.-Russia tensions are running high over Moscow's massive military buildup on the Ukrainian border.

Putin, meanwhile, proposed a new deal to supply China with natural gas, the media said, adding the two leaders voiced deep concern over Japan's plan to release treated radioactive water into the sea from the crippled Fukushima Daiichi nuclear power plant.

China and the Soviet Union, Russia's predecessor state, were competitors during the Cold War. They were at odds over interpretations and practical applications of Marxism-Leninism, the ideology of 20th-century communism.

The two nations, however, have been reinforcing cooperation lately, as their relations with the United States have deteriorated.

Putin participated in the opening ceremony of the Beijing Summer Olympics in 2008, while Xi took part in the one at the Sochi Winter Games in Russia in 2014.