China’s leader said his country and Russia were “true friends who have been through thick and thin together” after a video call with President Vladimir V. Putin on Monday, part of a pointed mutual affirmation of allegiance between Beijing and Moscow as President Trump has turned toward the Kremlin.

The warm words attributed to Xi Jinping in Chinese state media were clearly intended to dampen speculation that the Trump administration, which has pursued a rapid rapprochement with Russia, might succeed in driving a wedge between Beijing and Moscow.

The call came on the anniversary of Russia’s 2022 invasion of Ukraine, after three years in which China extended a lifeline to Russia by helping Mr. Putin weather economic isolation from the West and struggles on the battlefield.

Shortly before the invasion of Ukraine, Mr. Xi and Mr. Putin heralded a “no limits” partnership. Since then, China has sustained Russia’s war machine with oil purchases and exports of dual-use technologies.

Mr. Xi and Mr. Putin also share an ideological opposition to the West. They blame the United States for holding back their global ambitions, and promote a reshaping of the global order to weaken Washington’s dominance.

“History and reality show us that China and Russia are good neighbors who won’t move away, and true friends who have been through thick and thin together, support each other and develop together,” Mr. Xi was quoted as saying by Chinese state media.

Mr. Xi said relations between China and Russia were not “affected by any third party,” in what appeared to be an oblique reference to the United States. And he said the two countries’ foreign policies were there for the “long term.”

The Kremlin issued a similarly cordial statement after the call, describing Mr. Xi and Mr. Putin’s conversation as “warm and friendly.” In a rebuff of the idea that President Trump could divide the two countries, the Kremlin added: “The leaders emphasized that the Russian-Chinese foreign policy link is the most important stabilizing factor in world affairs,” and said the relationship was “not subject to external influence.”

The call was the second between Mr. Xi and Mr. Putin in just over a month, coming less than two weeks after Mr. Trump upended U.S. strategy toward Russia by holding a phone call with Mr. Putin and appearing to side with him over the war in Ukraine. Mr. Trump blamed Ukraine for instigating Russia’s invasion, called President Volodymyr Zelensky of Ukraine a “dictator” and excluded Kyiv from early-stage peace negotiations.

Mr. Trump’s decision to side so favorably with Mr. Putin on the war has fueled speculation that Washington was aiming to split Russia and China, a country that many senior Trump administration officials consider a far more serious threat to U.S. interests.

Some incoming officials in the Trump administration have suggested drawing down American troop levels in Europe, which serve as a bulwark against Russia, so Washington can focus its military efforts on defending against China.

Trump’s special envoy to Ukraine, Keith Kellogg, told a panel earlier this month in Munich that the Trump administration was hoping to “force” Mr. Putin to fray his ties with North Korea, Iran and China.

Analysts, however, have expressed skepticism that China and Russia can be driven apart in what is being called a “reverse Nixon,” a reference to President Nixon’s rapprochement with Beijing in 1972 that was aimed at exploiting the worsening relations between China and the Soviet Union.

Unlike 53 years ago, ties between China and Russia today are at a high, with few prospects for domestic political change in either country.

“There’s strategic and geopolitical alignment for this relationship,” said Sergey Radchenko, a professor at the Johns Hopkins School of Advanced International Studies who specializes in Chinese-Russian relations. “They don’t see eye to eye on everything, but I think they both realize they need each other.”

Mr. Radchenko said Beijing was probably feeling uncomfortable with Mr. Trump’s bid to court Mr. Putin, but that it was unlikely that Mr. Putin would see his interests better served by aligning more closely with the United States over China.

“The idea that Putin can be manipulated as some kind of weapon against China, I think that’s naïve on the part of the Trump administration,” he said.

How much China knew about Russia’s plans in the run-up to Mr. Putin’s invasion of Ukraine three years ago remains unclear.

A Western intelligence report issued shortly after the invasion concluded that senior Chinese officials had told senior Russian officials in early February not to invade Ukraine before the end of the Winter Olympics in Beijing. But the intelligence did not necessarily indicate that direct conversations about an invasion had taken place between Mr. Putin and Mr. Xi.

China has denied any prior knowledge of the invasion, and Beijing didn’t evacuate its embassy or citizens from Ukraine in the days before the start of the war.

“Assertions that China knew about, acquiesced to or tacitly supported this war are purely disinformation,” Qin Gang, the Chinese ambassador to the United States at the time, wrote in a March 2022 article in The Washington Post.

Mr. Xi is set to visit Moscow in May to attend the commemorations of the Soviet victory over Nazi Germany in World War II, according to Russian state media. Mr. Putin has also invited Mr. Trump.

The call on Monday between the Chinese and Russian leaders came as the Kremlin tries to keep its partner nations on its side, while pursuing a warming of relations with the United States, a country Mr. Putin has long derided as an irresponsible global superpower.

“The president last week spoke about his desire to inform a series of government partners about the contacts with the Americans,” the Kremlin’s spokesman, Dmitri S. Peskov, said in a call with reporters on Monday. “In line with those intentions, that process started today.”

The Kremlin added in a statement that Mr. Putin had informed Mr. Xi during their call about “recent Russian-American contacts.” It also said China had “expressed support for the dialogue between Russia and the United States that has begun, as well as readiness to contribute to the search for a peaceful settlement of the Ukrainian conflict.”

Mr. Putin also spoke with the leader of Tajikistan on Monday, and the Russian foreign minister, Sergei V. Lavrov, met with President Reycep Tayyip Erdogan of Turkey.

In the comments published by Chinese state media, Mr. Xi said he was “pleased” that Russia had started negotiations with “other parties” to end the “Ukrainian crisis.”

China has yet to describe Russia’s invasion of Ukraine as a “war.”

Amy Chang Chien contributed research.