- Trump and his team have signaled opposition to some of Ukraine's recent attacks on Russian soil.
- Trump's Ukraine envoy said this week that the killing of a Russian general was outside the rules of war.
- Trump has also criticized Biden's decision to allow strikes on Russia using US-supplied missiles.
In a worrying sign for Ukraine, the incoming Trump administration has signaled its disapproval of recent attacks on Russian soil, including long-range strikes and the assassination of a top general in Moscow using a scooter bomb.
President-elect Donald Trump's envoy to Ukraine, retired Lt. Gen. Keith Kellogg, said on Wednesday that Ukraine's claimed killing of Lt. Gen. Igor Kirillov this week was contrary to the rules of war.
Kirillov, who headed up Russia's chemical, nuclear, and biological protection troops, was killed by a bomb planted on a scooter in Moscow on Tuesday. Ukraine has claimed responsibility.
Speaking on Fox Business, Kellogg said, "There are rules of warfare and there are certain things you just kind of don't do."
He added: "When you're killing flag officers, general officers, admirals or generals in their hometown, it's kind of like you've extended it, and I don't think it's really smart to do it."
Russia said it had arrested a man in connection with the killing, saying he was suspected of a "terrorist attack," the BBC reported.
Kellogg said the events wouldn't be a setback for any peace talks.
The US State Department said it was unaware of the plot, with an unnamed official saying the US doesn't support this kind of action, according to Agence France-Presse.
Kellogg's remarks come after President-elect Donald Trump said on Monday that the decision to allow Ukraine to make long-range strikes on Russia with US-supplied missiles was "stupid," and that he might reverse it once in office.
"I don't think they should have allowed missiles to be shot 200 miles into Russia," he said. "I think that was a bad thing."
Trump claimed that the decision prompted North Korea to send troops to fight alongside Russia, though intelligence agencies said that North Korean troops were being deployed at least two weeks before the Biden administration's decision.
He also said that the Biden administration should have asked for his opinion "weeks before I take over."
"Why would they do that without asking me what I thought?" he added.
Trump has repeatedly stated he would end the war in Ukraine, without publicly saying how he would achieve it.
Plans under discussion have included establishing a demilitarized zone in the areas occupied by Russia and requiring a pledge from Ukraine not to join NATO, The Wall Street Journal reported in November.
In an interview with Le Parisien on Monday, Ukrainian President Volodymyr Zelenskyy reiterated his stance that ceding territory to Russia in any talks would be unacceptable, along with any promise not to join NATO.