The Republican senator Tom Cotton refused four times on Sunday to condemn or even comment on Donald Trump’s repeated praise for Vladimir Putin, the Russian president who ordered the invasion of Ukraine.

“If you want to know what Donald Trump thinks about Vladimir Putin or any other topic,” Cotton told ABC’s This Week, “I’d encourage you to invite him on your show. I don’t speak on behalf of other politicians. They can speak for themselves.”

The former president’s views are clear. Trump has repeatedly praised Putin and though at CPAC on Saturday he condemned the invasion, he again called the Russian leader “smart”.

Cotton, from Arkansas, is a military veteran and foreign policy hawk with reputed presidential ambitions from the hard Republican right. His host on ABC, George Stephanopoulos, tried repeatedly to prise comment from him. Cotton was happy to condemn Putin and praise Ukrainian bravery – and to criticise US allies in Europe.

“I know that they say they sanctioned 80% of the banks in Russia,” he said. “Well, Vladimir Putin controls 100% of the banks in Russia. He can use the other 20% to continue to finance his war machine.

“It’s time to remove all Russian financial institutions from the international payment system. It’s time to impose sanctions on his oil and gas exports, which he uses as his primary means of financial support.”

Stephanopoulos cited Trump calling Putin “smart” and “savvy” and “say[ing] Nato and the US are dumb”, and asked: “Are you prepared to condemn that kind of rhetoric from the leader of your party?”

Cotton said: “George, you heard what I had to say about Vladimir Putin. That he is a ruthless dictator who’s launched a naked, unprovoked war of aggression.

“Thankfully, the Ukrainian army has anti-tank missiles that President Obama would not supply, that we did supply last time Republicans were in charge in Washington. That’s why it’s so urgent that we continue to supply those weapons to Ukraine.”

Stephanopoulos asked: “Why can’t you condemn Donald Trump for those comments?”

Cotton said: “George, if you want to know what Donald Trump thinks about Vladimir Putin or any other topic, I’d encourage you to invite him on your show. I don’t speak on behalf of other politicians. They can speak for themselves.

“I speak on behalf of Arkansans, who I talked to this week and who are appalled at what they saw in Ukraine and they want me right now to fight in Washington to support those brave Ukrainians.”

Stephanopoulos said: “You’re a senior member of the Republican party. Donald Trump is the leader of the Republican party. He said last night again, suggested that he’d be running for president. When Fox News asked him if he had a message for Vladimir Putin, he said he has no message.

“Why can’t you condemn that? I feel quite confident that if … a Barack Obama or Joe Biden said something like that, you’d be first in line to criticise him.”

Cotton said: “Again, George, if you want to talk to the former president about his views or his message, you can have him on your show.

“My message to Vladimir Putin is quite clear. He needs to leave Ukraine unless he wants to face moms and teenagers with Molotov cocktails and grandmothers and grandfathers with AK-47s for years to come.”

Stephanopoulos varied his line of attack, asking: “If Donald Trump runs again, can you support him?”

But Cotton wasn’t for picking.

“George,” he said, “I’m not worried about this fall’s elections right now, much less an election two years from now. I’m focused on the naked war of aggression that Vladimir Putin has launched in Ukraine right now. There’s not a moment to lose. We can worry about electoral politics down the road.”

Stephanopoulos tried once more.

“Former President Trump was out there talking about it last night. I simply don’t understand why you can’t condemn his praise of Vladimir Putin.”

“George,” said Cotton, “again, I don’t speak on behalf of other politicians. They can all speak for themselves.”

Cotton’s refusal to criticise Trump – who has few critics in Congress and retains control of the Republican party – was not unique among Republicans but it was widely noted online.

Reed Galen, a former Republican strategist now part of the anti-Trump Lincoln Project, wrote: “Tom Cotton is wily, like a Fennec fox. He’ll come up, look around, listen, then skitter back into his hole until the time is right.”