As American and North Korean missiles are dueling for supremacy in Ukraine, President Putin is threatening a nuclear war. 

“It will be North Korean versus U.S. missiles,” a senior researcher at the Korea Institute for Defense Analyses, Lee Soo-hoon, said, pointing to self-propelled howitzers and rockets with a range of 40 miles that North Korea is bringing to the battlefield. 

As the war escalates with the insertion of thousands of North Korean troops fighting for the Russians, President Putin has made Ukrainians firing American-made missiles a pretext for raising the threat level of a nuclear reprisal. 

Russia will “engage in nuclear deterrence against those countries that offer their territory, maritime zones, airspace, and resources for aggression against it,” the Russian news agency, Tass, said in explaining Mr. Putin’s response to President Biden’s decision authorizing Ukrainian forces to fire American-made missiles as far as 300 kilometers, or nearly 200 miles, into Russian territory. 

Mr. Putin, Tass said, “decreed to update the country’s nuclear doctrine” by authorizing nuclear deterrence aimed at “a potential adversary, which may encompass individual countries and military alliances” that see Russia “as a potential enemy and possess nuclear and/or other weapons of mass destruction, or have substantial combat capabilities of general-purpose forces.” 

As if to dramatize Mr. Putin’s expanded nuclear doctrine, Tass reported that Russian forces had shot down five American-made missiles and damaged a sixth about 70 miles inside Russia. Tass said the missiles were ATACMs, the acronym for the American Army Tactical Missile System. They all fell harmlessly, Tass said. 

All of the Ukrainian forces’ missiles won’t necessarily be American, either. France and Britain are considering shipping missiles to Ukraine.

“Debates are already raging about allowing the use of Western missiles against Russian territory,” a French newspaper, Le Figaro, said in an updated version of an initial report that said France and Britain had authorized use of their missiles in Ukraine. The paper quoted the French president, Emmanuel Macron, as having spoken “in favor of this during a stated visit to Germany in May.”

The Guardian reported that Britain is likely to ship  to Ukraine Storm Shadow missiles with a range of 250 kilometers, or 155 miles.

Britain’s prime minister, Keir Starmer, at the Rio de Janeiro meeting of G20 leaders, declared, “We cannot allow Putin to win this war,” according to the Guardian. “We need to double down,” he said, “to make sure Ukraine has what is necessary for as long as necessary.” Mr. Macron said Mr. Biden’s decision on missiles for Ukraine was “a totally good one.”

In a bitter disappointment for Ukraine, though, Germany’s chancellor, Olaf Scholz, has flatly rejected calls for Germany to add its Taurus cruise missiles to the mix in the Ukrainian inventory.

The German broadcaster Deutsche Welle, widely known as DW, reported Mr. Scholz was concerned about their range — long enough to possibly reach Moscow — and the need for German troops to accompany them.

“What is being done in the way of target control on the part of the British and the French can’t be done in Germany,” DW quoted Mr. Scholz as saying. “Everyone who has dealt with this system knows that.”

Mr. Scholz  was just as emphatic about the need for German troops to stay out of the wa: “German soldiers can at no point and in no place be linked with the targets that this [Taurus] system reaches,” he reportedly said.

The G20 came out with a carefully bland statement that called for peace without blaming anyone for war in Ukraine. That was just fine with Russia’s foreign minister, Sergey Lavrov, who had no trouble signing it in the absence of Mr. Putin, who technically could be arrested under a warrant issued by the International Criminal Court if he ventures on to foreign soil.Washington was much more emphatic. “The fire was lit by Russia’s invasion of Ukraine,” the deputy national security adviser, Jon Finer, said. “This notion of fuel on the fire is, frankly, a side issue to the main issue, which is Russia waging a war of aggression across a sovereign border.”