Moscow sees no possibility of a diplomatic solution to end the war in Ukraine and expects a long conflict, a senior Russian diplomat has warned, as President Vladimir Putin’s full-scale invasion reaches the six-month mark this week.

Gennady Gatilov, Russia’s permanent representative to the UN in Geneva, told the Financial Times that the UN should be playing a bigger role in attempts to end the conflict and accused the US and other Nato countries of pressing Ukraine to walk away from negotiations. There would be no direct talks between Putin and Ukraine’s president Volodymyr Zelenskyy, he said.

“Now, I do not see any possibility for diplomatic contacts,” Gatilov said. “And the more the conflict goes on, the more difficult it will be to have a diplomatic solution.”

His remarks, which come despite a flurry of shuttle diplomacy in recent weeks, are a blow to negotiators who had hoped that a recent agreement on grain exports from Ukraine’s Black Sea ports could form the basis for a broader deal.

The UN has become mired in “politicisation” because of the war and that has “damaged the authority of the UN and its organisations”, Gatilov said. As a result, it is unable to act effectively as a mediator, he complained.

“We do not have any contacts with the western delegations,” he said of his day-to-day work in Geneva. “On the protocol side we do not see each other . . . Privately we do not have any contacts, unfortunately . . . we simply do not talk to each other.”

Global diplomacy was in the worst state he had experienced in his 50-year career, Gatilov added. “The world has changed and the UN will never be the same as it was before,” he said.

Russia invaded on February 24, in what Putin called a “special military operation” to “denazify” Ukraine. It was condemned by western countries which imposed crippling sanctions on Moscow and severed ties. An initial attempt to seize Kyiv in a lightning assault was thwarted, forcing Moscow’s army to regroup and focus on an artillery-led campaign in the east.

Bilateral ceasefire negotiations broke down after evidence was discovered of war crimes committed by occupying Russian troops in April. Moscow has denied the allegations.

The failure to restart peace talks, combined with continued western military support for Ukraine, meant it was impossible to forecast how long the conflict could last, Gatilov said: “And so they [Kyiv and its western supporters] will fight until the last Ukrainian.”

Gatilov, who served as deputy foreign minister before being posted to Geneva in 2018, claimed that Moscow and Kyiv had been “very close” to an agreement that could have paused the conflict in negotiations hosted by Turkey in April. People involved in the talks have refuted this.

The UN and Turkey have sought to act as intermediaries between Kyiv and Moscow, and had recent success in brokering the deal on Ukraine’s grain exports.

But Gatilov said it was “unfortunate” that the UN was not playing a larger role. “I think [the grain deal] is the only example that they played a practical role in trying to mediate,” he said. “It should be more than that.”

Gatilov accused western countries of using the situation “as a matter of pressure on Russia, as a tool of isolation of Russia . . . damaging our position, economically, politically”.

“They do not care about the Ukrainian people, the Ukrainian soldiers,” he said.

Ukraine’s defence has been boosted by more than $30bn worth of weapons supplies pledged by the US, UK and other Nato allies. Zelenskyy has previously said that he saw direct talks with Putin as the only way to negotiate an end to the conflict, and only after a Russian withdrawal from all Ukrainian territory captured since February.

Mykhailo Podolyak, an adviser in Zelenskyy’s administration who participated in the failed peace talks, said on Friday that “negotiating with the Russian Federation means . . . a fatal ending for everyone”.

Turkey’s president Recep Tayyip Erdoğan, who has maintained relations with both Kyiv and Moscow since the invasion, visited Putin in Sochi earlier this month and met Zelenskyy in Lviv last week alongside UN secretary-general António Guterres in an effort to act as a mediator.

Erdoğan said during his visit to Ukraine: “I continue to have faith that the war will end at the negotiating table. Mr Zelenskyy and Mr Putin are of the same opinion.”

But that statement did not refer to any new developments that could lead to negotiations, according to a person familiar with the discussions.

Gatilov praised Erdoğan for “trying his best” to facilitate dialogue but dismissed speculation of direct talks between Putin and Zelenskyy, saying there “was not any practical platform for having this meeting”.

He also accused Ukraine of “a clear provocation” at the Zaporizhzhia nuclear plant which is occupied by Russian forces. Ukraine has blamed Russia for shelling the plant, while Nato has said Russia is using the nuclear site as a base from which to launch attacks.

“Russian troops are just guarding it. Just securing it. Why should we shell it?” Gatilov said. Russia has agreed to an urgent safety visit by the International Atomic Energy Agency to the plant.

Additional reporting by Roman Olearchyk and Mehul Srivastava in Kyiv