Japanese Prime Minister Fumio Kishida lays the flowers at a church in Bucha, a town outside Kyiv that became a symbol of Russian atrocities against civilians, in Ukraine on Tuesday. Iori Sagisawa/Kyodo News via Associated Press

KYIV, Ukraine — Prime Minister Fumio Kishida made a surprise visit Tuesday to Kyiv, stealing some of the attention from Asian rival President Xi Jinping of China, who met in Moscow with Russian President Vladimir Putin to promote Beijing’s peace proposal for Ukraine that Western nations have already criticized.

Japanese Prime Minister Fumio Kishida and Ukrainian President Volodymyr Zelensky greet each other after the signing of joint documents in Kyiv, Ukraine, on Tuesday. Efrem Lukatsky/Associated Press

The two visits, about 500 miles apart, highlighted the nearly 13-month-old war’s repercussions for international diplomacy as countries line up behind Moscow or Kyiv. Kishida, who will chair the Group of Seven summit in May, met President Volodymyr Zelensky and paid tribute to those killed in Bucha, a town outside Kyiv that became a symbol of Russian atrocities against civilians.

After talks with Xi, Putin said a Chinese peace plan could provide a basis for a settlement of the fighting in Ukraine when the West is ready for it, but he added that Kyiv’s Western allies have shown no interest in that.

U.S. officials have said any peace plan coming from the Putin-Xi meeting would be unacceptable because a cease-fire would only ratify Moscow’s territorial conquests and give Russia time to plan for a renewed offensive.

“It looks like the West indeed intends to fight Russia until the last Ukrainian,” Putin said, adding the latest threat is a British plan to give Ukraine tank rounds containing depleted uranium.

“If that happens, Russia will respond accordingly, given that the collective West is starting to use weapons with a nuclear component,” he said, without elaborating.

Putin has occasionally warned that Russia would use all available means, including possibly nuclear weapons, to defend itself, but also has sometimes backed off such threats.

Putin’s comment referred to remarks Monday by U.K junior Defense Minister Annabel Goldie, who wrote: “Alongside our granting of a squadron of Challenger 2 main battle tanks to Ukraine, we will be providing ammunition, including armor-piercing rounds which contain depleted uranium. Such rounds are highly effective in defeating modern tanks and armored vehicles.”

Russian Foreign Minister Sergey Lavrov said the U.K. plan shows that the British “have lost the bearings,” and Defense Minister Sergei Shoigu said “it marked another step, and there aren’t so many of them left.”

Japanese Prime Minister Fumio Kishida gets in a car after his visit to a church in Bucha, a town outside Kyiv that became a symbol of Russian atrocities against civilians, in Ukraine on Tuesday. Iori Sagisawa/Kyodo News via Associated Press

But weapons expert Hamish de Bretton-Gordon, former commander of Britain’s Royal Tank Regiment, said it was “reckless” of Putin “to try and suggest Britain is sending nuclear material” to Ukraine. He said depleted uranium is a common component of tank rounds, possibly even used by Russia.

“Putin insinuating that they are some sort of nuclear weapon is bonkers,” de Bretton-Gordon told the Associated Press. “Depleted uranium is completely inert. There is no way that you could create a nuclear reaction or a nuclear explosion with depleted uranium.”

Beijing insists it is a neutral broker in Ukraine, and Xi said Tuesday after his talks with Putin: “We adhere to a principled and objective position on the Ukrainian crisis based on the goals and principles of the U.N. Charter.” He added that the Chinese plan seeks to “actively encourage peace and the resumption of talks.”

In a joint statement, Russia and China emphasized the need to “respect legitimate security concerns of all countries” to settle the conflict, echoing Moscow’s argument that it sent troops into its neighbor to prevent the U.S. and its NATO allies from turning the country into an anti-Russian bulwark.

“Russia welcomes China’s readiness to play a positive role in the political and diplomatic settlement of the Ukrainian crisis” and the “constructive ideas” contained in Beijing’s peace plan, the statement said. It added: “The parties underline that a responsible dialogue offers the best path for a lasting settlement … and the international community should support constructive efforts in this regard.”

After meeting Kishida, Zelensky told reporters his team had sent his own peace formula to China but hasn’t gotten a response, adding that there were “some signals, but nothing concrete about the possibility of a dialogue.”

Kishida called Russia’s invasion a “disgrace that undermines the foundations of the international legal order.”

Earlier he laid flowers at a church in Bucha for the town’s victims.

“Upon this visit to Bucha, I feel a strong resentment against cruelty,” he said. “I would like to represent the people in Japan, and express my deepest condolences to those who lost their loved ones, were injured as a result of this cruel act.”

U.S. Ambassador to Japan Rahm Emanuel noted the “two very different European-Pacific partnerships” that unfolded Tuesday.

“Kishida stands with freedom, and Xi stands with a war criminal,” Emanuel tweeted, referring to Friday’s decision by the International Criminal Court to issue an arrest warrant for Putin, saying it wanted to put him on trial for the abductions of thousands of children from Ukraine.

Kyiv’s allies pledged more support. Washington is accelerating its delivery of Abrams tanks to Ukraine, sending a refurbished older version that can be ready faster, U.S. officials told the Associated Press. The aim is to get the 70-ton behemoths to the war zone in eight to 10 months, the officials said on the condition of anonymity because the plan was not announced.

The Russia-China front against the West was a prominent theme of Xi’s visit. Russia’s Deputy Foreign Minister Sergei Ryabkov accused NATO of seeking to become the world’s dominant military force. “That is why we are expanding our cooperation with China, including in the security sphere,” he said.

Putin is keen to show he has a heavyweight ally and market for Russian energy products under Western sanctions. He said he wants to expand bilateral economic ties, noting Russian-Chinese trade rose by 30% last year to $185 billion and is expected to top $200 billion this year.

Russia stands “ready to meet the Chinese economy’s growing demand for energy resources” by boosting deliveries of oil and gas, he said, while listing other areas of economic and cultural cooperation, including aircraft and shipbuilding industries and other high-tech sectors.

Whether China will provide military support is a key question. Western officials “have seen some signs” Putin also wants lethal weapons from Beijing, though there is no evidence it has granted his request, NATO Secretary-General Jens Stoltenberg said in Brussels.

Meeting with Russian Prime Minister Mikhail Mishustin, Xi said he invited Putin to China this year to discuss a regional initiative that seeks to extend Beijing’s influence through economic cooperation.

Moscow and Beijing have both weathered international condemnation of their human rights records. The Chinese government has been widely condemned for alleged atrocities against Uighur Muslims in its far western Xinjiang region. The allegations include genocide, forced sterilization and the mass detention of nearly 1 million Uighurs. Beijing has denied the allegations.

Kishida rode a train from Poland to Kyiv just hours after he met with Indian Prime Minister Narendra Modi in New Delhi and a week after a breakthrough summit with South Korean President Yoon Suk Yoel.

Both China and Japan have enjoyed recent diplomatic successes that emboldened their foreign policy.

Japan, which has territorial disputes over islands with both China and Russia, is particularly concerned about the Beijing-Moscow relationship. Both nations have conducted joint military exercises near Japan’s coasts.

Beijing’s diplomatic foray follows its recent success in brokering a deal between Iran and its chief Middle Eastern rival, Saudi Arabia, to restore relations after years of tensions. The move displayed China’s influence in a region where Washington has long been the major foreign player.

Kishida, the only G-7 leader who hadn’t visited Ukraine, and was under domestic pressure to do so. He became Japan’s first postwar leader to enter a war zone.

Due to its pacifist principles, Japan’s support for Ukraine has been limited to nonlethal equipment and humanitarian supplies. It has contributed more than $7 billion to Ukraine and accepted more than 2,000 displaced Ukrainians, despite its strict immigration policy.

Tokyo joined the U.S. and European nations in sanctioning Russia over the invasion. By contrast, China has refused to condemn Moscow’s aggression and criticized Western sanctions against Moscow, while accusing NATO and Washington of provoking Putin’s military action.

Japan was quick to react because it fears the possible impact of a war in East Asia, where China’s military has grown increasingly assertive and has escalated tensions around self-ruled Taiwan, which Beijing claims as its territory.

In Beijing, Foreign Ministry spokesperson Wang Wenbin said of Kishida’s trip: “We hope Japan could do more things to deescalate the situation instead of the opposite.”

Associated Press writers Mari Yamaguchi in Tokyo, Lolita C. Baldor in Washington and Jill Lawless in London contributed.