MOSCOW (Reuters) -President Vladimir Putin said on Friday that Russian forces advancing in Ukraine's northeast were carving out a buffer zone to protect Russia from attacks and said the West was "sick in the head" if it thought it could dictate terms to Moscow.

Speaking to reporters on a state visit to China after discussing Ukraine during talks with Xi Jinping, Putin said that Russian troops were advancing to plan after repeated deadly Ukrainian strikes on the Belgorod region of Russia.

"As for what is happening in the Kharkiv direction. This is their (Ukraine's) fault because they shelled and continue, unfortunately, to shell residential neighbourhoods in the border areas, including Belgorod," Putin said.

"Civilians are dying there. It's obvious. They are shooting directly at the city centre, at residential areas. And I said publicly that if this continues, we will be forced to create a security zone, a buffer zone. That is what we are doing."

When asked if Russian forces planned to take control of nearby Kharkiv, Ukraine's second-biggest city, Putin said:

"As for Kharkiv, there are no such plans as of today."

Russia last week opened a new front in the Ukraine war by pushing swiftly over the border into northeastern Ukraine with small groups of highly mobile units, a move that has forced Ukraine to rush in troops from other areas.

Putin sent tens of thousands of troops into Ukraine in 2022, triggering the biggest land war in Europe since World War Two. The conflict in eastern Ukraine began in 2014 after a pro-Russian president was toppled in Ukraine's Maidan Revolution and Russia annexed Crimea, with Russian-backed forces fighting Ukraine's armed forces.

PEACE?

Putin said he had discussed many important questions with Xi including Ukraine, and that Xi had relayed details about discussions he had during his own trip to Europe. He praised Xi for taking a flexible approach to finding an end to the conflict.

But Putin scolded the West whom he blames for sinking a draft ceasefire which Russian and Ukrainian negotiating teams reached in Turkey in 2022.

"They wanted to gain the advantage on the battlefield, achieve strategic defeat but it didn't work out," Putin said of the West and Ukraine. "Are they sick in the head?"

He said the failed 2022 negotiations were a possible basis for peace, though he said any ceasefire would have to take into account the reality on the ground - where Russia controls about 18% of Ukrainian territory.

"Of course, we shall proceed from the reality taking shape on the ground. That goes without saying," Putin said.

Russia, he said, suspected that a planned June summit that Switzerland hopes will pave the way for a peace process in Ukraine was aimed at producing an ultimatum to Russia.

He said Russia was prepared to talk but had not been invited. Asked under what conditions he would be ready to participate in the Swiss conference, he said politics was about concrete realities, not hypothetical situations.

"But we are ready to discuss (peace) - we never refused to," Putin said.

Any possible deal, he said should only be signed with the "legitimate authorities" of Ukraine.

(Reporting by ReutersEditing by Andrew Osborn and Sharon Singleton)

By Guy Faulconbridge