After announcing that there will indeed be a US-Russia summit in the coming weeks, National Security Adviser John Bolton issued a challenge to the sceptical scrum of reporters at his Moscow press conference. “I’d like to hear someone say this is a bad idea,” he said.

Bolton’s argument is simple. He assured reporters that US positions on Russia’s sovereignty over Crimea (not recognised) and sanctions on Moscow (still in effect) had not changed. He acknowledged that the bilateral relationship is at a low point. Nevertheless, he said, a meeting between Vladimir Putin and Donald Trump could lead to co-operation on areas of mutual interest. In essence, he asked: what’s wrong with talking?

As an admirer of Bolton’s tough-minded writings on Putin when he was out of government, allow me to take up the challenge and explain why a Putin-Trump summit is a bad idea.

There are many reasons, but the most important concerns the current American president.

Just look at his track record. Last summer, when Trump met with Putin on the sidelines of the G20 summit in Germany, he briefly agreed to a US-Russian cybersecurity task force, an idea as ridiculous as an anti-narcotics commission headed by El Chapo.

Under pressure from his own Cabinet and fellow Republicans, Trump walked it back the next day.

In March, Trump famously congratulated Putin for winning his rigged election, despite notes from aides for the call that said: “Do Not Congratulate.”

In interviews, Trump has sounded like Noam Chomsky when confronted with Putin’s many crimes. Remember the Fox News interview last year when he was asked why he “respects” Putin, given his government’s role in the murder and disappearance of journalists and opposition figures? “You think our country’s so innocent?” Trump responded.

If Bolton were leading the summit with Putin, the US would be in good hands. He understands that Putin is a liar and a killer.

Indeed, Bolton wrote last summer that Putin had lied to Trump when he insisted Russia did not interfere in the 2016 election. Trump, meanwhile, said in November that he believed Putin’s denial after their second meeting. (Trump has since conceded that Russia did interfere.)

And this is the point. Trump has a blind spot when it comes to Putin, and it’s dangerous for the two men to be in any kind of negotiation.

This is not a roundabout way of saying that Trump is guilty of collusion; we should all reserve judgment on this matter until the completion of Robert Mueller’s investigation.

Nor is this a challenge to his constitutional authority as commander-in-chief.

But just because you can do something, doesn’t mean you should. For Trump, meeting with Putin now, at this moment, is a horrendous idea.

Remember it was only a little more than three months ago that Russia was fingered for deploying a nerve agent against one of its former spies residing in the UK.

At the very least, Trump should demand that Putin account for that crime, only the latest of many, before agreeing to meet with him.

Thankfully, Trump’s government has consistently taken a much tougher line on Russia than he himself has. The US approved the sale of defensive weapons to Ukraine, which continues to fight Russian-backed separatists in the eastern part of the country.

It has imposed tough sanctions on Russian oligarchs and maintained the ones imposed by Trump’s predecessor for Russia’s annexation of Crimea. And the US has supported the integration of Montenegro into Nato and deployed forces to the Baltic States bordering Russia to deter any future adventurism Putin may have in mind.

All of this has made for a Janus-faced approach to Russia. The danger is that, in the context of a summit, all of these tough policies are negotiable. And that’s frightening.

As long as Putin is in charge at the Kremlin, Russia will be a threat to the US and its allies, not to mention the institutions and agreements that make up the liberal international order. Trump’s Cabinet understands this. The President, unfortunately, does not.

Eli Lake is a Bloomberg Opinion columnist covering national security and foreign policy