Vlodomyr Zelensky is angry about it. Vladimir Putin plots to abuse it. Boris Johnson warns against it. America prefers a Ukrainian victory — and yet, egged on by former officials and other believers in the United Nations’s magical powers, Antonio Guterres is launching a mission to mediate between Russia and Ukraine. 

The United Nations secretary-general visited Ankara today on his way to meet Mr. Putin at the Kremlin tomorrow. Afterwards Mr. Guterres plans to travel to Kyiv.  

Mr. Guterres’s trip was announced last week after a group of former top UN officials warned that unless he takes the diplomatic lead in Ukraine, the UN will become irrelevant and even may be dissolved.

A spokesman for Mr. Guterres, Farhan Haq, said today that the UN chief “thinks there is an opportunity now” for a peace initiative. “A lot of diplomacy is about timing,” Mr. Haq added, but declined to explain why Mr. Guterres believes now is the right time.  

The government at Kyiv, for one, is far from welcoming Mr. Guterres’s initiative.

“It is simply wrong to go first to Russia and then to Ukraine,” President Zelensky told reporters over the weekend. “There is no justice and no logic in this order.” A top aide to Mr. Zelensky, Igor Zhovkva, told NBC on Sunday that Ukraine has not authorized Mr. Guterres to mediate with Russia. 

Kyiv has surprised American and European leaders with its military’s unexpected resilience, so at this stage Washington seems to prefer a Ukrainian victory to diplomacy leading to a stalemate. 

Mr. Zelensky “has the mindset that they want to win, and we have the mindset that we want to help them win,” Secretary of Defense Austin told reporters today after visiting Kyiv. America wants to see “Russia weakened to the degree that it can’t do the kinds of things that it has done in invading Ukraine,” the secretary, a four-start general, added.  

Moscow is also taking a hard line. After the sinking of the Russian Navy’s Black Sea flagship, the Moskva, Mr. Putin reportedly decided to eschew mediation attempts. “Vladimir Putin has lost interest in diplomatic efforts to end his war with Ukraine and instead appears set on seizing as much territory as possible,” the Financial Times reported Sunday. 

Prime Minister Johnson, who has emerged as the foreign leader most admired in Ukraine, warned Mr. Guterres against becoming a tool in Mr. Putin’s propaganda machine, according to the Daily Telegraph.    

The UN’s Mr. Haq dismissed that critique, saying Mr. Guterres has been “involved in international politics for quite a long time,” which will prevent him from being manipulated by Mr. Putin. 

In early April, Mr. Zelensky urged the 15-member UN Security Council to expel Russia, or else “dissolve yourself.” That admonition was the apparent trigger to a letter from 200 former UN officials to Mr. Guterres, urging him to make a major initiative to end the war, or risk the dissolution of the UN.

The letter, according to a knowledgeable diplomat, was initiated by two of its signatories: a former State Department official, Jeffrey Feltman, who had served as the UN undersecretary general for political affairs, and a former UN assistant secretary general for human rights, Andrew Gilmore, a Briton. 

We “implore you to intensify your personal efforts, deploying all capabilities at your disposal and acting upon lessons learnt from previous conflicts, for the cessation of hostilities and conflict resolution through peaceful means,” the former officials wrote.

The UN “is being tested again in this case,” the signatories added. “We are horrified at the alternative, the UN becoming increasingly irrelevant and, eventually, succumbing to the fate of its predecessor, the League of Nations.”

Mr. Guterres’s spokesman, Stephane Dujarric, denied that the letter pushed Mr. Guterres to launch his current mission. Such trips “are not cooked up in some lab in a few hours,” Mr. Dujarric said, adding that although the letter-signers acted out of good will, they “don’t know what may be going on behind the scenes.”

Mr. Guterres is far from the first world leader to attempt to use what is known at Turtle Bay as his “good offices” to mediate a diplomatic ending to the Ukraine war. 

President Erdogan of Turkey has conducted several rounds of talks with Kyiv and Moscow. Today Mr. Erdogan expressed support for the new UN  diplomacy. Yet, Ankara has also taken sides by blocking Russian ships’ entry to the Black Sea and denying Russia use of Turkey’s airspace to transfer troops from Syria to Ukraine. 

Prime Minister Bennett of Israel traveled to Moscow early on for talks with Mr. Putin, and spoke often with Mr Zelensky. The president of Ukraine welcomed Israel’s mediation and even suggested a Russian-Ukrainian summit in Jerusalem.

More recently, however, Israel suspended its attempt at negotiating. Instead, it condemned Russia’s violations of human rights and upped its support of Ukraine. Mr. Guterres, in contrast, has joined the mediation game late.