Russian President Vladimir Putin, after talking with China’s Xi Jinping and India’s Narendra Modi, said on Monday the issue of NATO's eastward enlargement would have to be addressed for there to be sustainable peace in Ukraine.

Putin ordered tens of thousands of troops to invade Ukraine in February 2022 after eight years of fighting in eastern Ukraine between Russian-backed separatists and Ukrainian troops. Russia currently controls a little under one fifth of Ukraine.

Ukraine and Western European powers describe the invasion as a brutal imperial-style land grab. Putin casts the war as a battle with a declining West, which he says humiliated Russia after the Berlin Wall fell in 1989 by enlarging NATO eastwards.

On the sidelines of the Shanghai Cooperation Organisation (SCO) meeting in Tianjin, Modi held Putin's hand as they walked towards Chinese President Xi. All three smiled as they spoke, surrounded by translators.

Speaking at the summit, Putin said the West had tried to bring Ukraine into the West's orbit and then sought to entice the former Soviet republic into the US-led NATO military alliance.

"In order for a Ukrainian settlement to be sustainable and long-term, the root causes of the crisis, which I have just mentioned and which I have repeatedly mentioned before, must be eliminated," Putin said.

"A fair balance in the security sphere" must be also restored, Putin said, shorthand for a series of Russian demands about NATO and European security.

At the 2008 Bucharest summit, NATO leaders agreed that Ukraine and Georgia would one day become members. Ukraine in 2019 amended its constitution committing to the path of full membership of NATO and the European Union.

Reuters reported in May that Putin's conditions for ending the war include a demand that Western leaders pledge in writing to stop enlarging NATO eastwards and lift a chunk of sanctions on Russia.

Putin said that the "understandings" he reached with US President Donald Trump at a summit in Alaska in August opened a way to peace in Ukraine, which he would discuss with leaders attending the regional summit in China.

"We highly appreciate the efforts and proposals from China and India aimed at facilitating the resolution of the Ukrainian crisis," Putin told the forum.

"The understandings reached at the recent Russia–US meeting in Alaska, I hope, also contribute toward this goal."

He said he had detailed to Xi on Sunday the achievements of his talks with Trump and the work "already underway" to resolve the conflict and would provide more detail in two-way meetings with the Chinese leader and others.

China and India are by far the biggest purchasers of crude from Russia, the world's second-largest exporter. Trump has imposed additional tariffs on India over the purchases but there is no sign yet that either India or China are going to stop purchasing Russian oil, a key export of Russia's war economy.