In a joint statement at the end of President Xi Jinping's state visit to Moscow, the two men cautioned against any steps that might push the Ukraine conflict into an "uncontrollable phase", adding pointedly that there could be no winners in a nuclear war.

Putin accused Western powers of fighting "to the last Ukrainian", while Xi reiterated China's "neutral position" on Ukraine and called for dialogue.

"We believe that many of the provisions of the peace plan put forward by China are consonant with Russian approaches and can be taken as the basis for a peaceful settlement when they are ready for that in the West and in Kyiv. However, so far we see no such readiness from their side," Putin said.

China's proposal - a 12-point paper calling for a de-escalation and eventual ceasefire in Ukraine - lacks details on how to end the war.

The United States has been dismissive of China's proposal, given Beijing's refusal to condemn Russia over Ukraine, and says a ceasefire would lock in Russian territorial gains and give Putin's army more time to regroup.

Ukraine has welcomed China's diplomatic involvement but says Russia must pull out its troops and underlines the importance of Ukraine's territorial integrity.

The Kremlin talks were intended to cement the "no limits" partnership the two leaders announced last February, less than three weeks before Russia invaded Ukraine.

They signed a series of documents on a "strategic co-operation" after what Putin described as "successful and constructive" talks showing China was clearly now Russia's most important economic partner.

Xi's state visit is a major boost to Putin as he squares off against what he sees as a hostile West bent on inflicting a "strategic defeat" on Russia.

The Chinese leader visited Moscow days after an international court issued an arrest warrant for Putin over Russia's actions in Ukraine, where Russian forces have made little progress in recent months despite suffering heavy losses.

In their statement on Tuesday, Xi and Putin also called on the United States to stop "undermining global strategic security" and to cease developing a global missile defence system.

While pledging more regular joint military drills, however, the two leaders said the closer relationship between the two countries was not directed against any third nation and it did not constitute a "military-political alliance".

Putin said Russia, China and Mongolia had completed "all agreements" on finishing Russia's coveted pipeline to ship Russian gas to China, and Moscow was ready to increase oil exports to Beijing.

But a joint statement after the talks said only that the parties involved in the pipeline, which Putin has called "the deal of the century", "will make efforts to advance work on the study and approval" of the pipeline.

Russia's Deputy Prime Minister Alexander Novak told reporters there were still details that need to be worked out.

Australian Associated Press