Despite showing signs of desperation in Russia’s war against Ukraine, Russian President Vladimir Putin has no interest in negotiating an end to the conflict, U.S. Secretary of State Antony Blinken said in an interview that aired Thursday morning.

Speaking to ABC’s “Good Morning America,” Blinken noted that Ukrainian President Volodymyr Zelenskyy has said the war will end at some point through diplomacy.

“But what we've seen thus far is no interest on the part of Putin in meaningful diplomacy,” Blinken said.

The point might be moot anyway. Last month, after Putin signed treaties to illegally annex four Moscow-occupied territories in Ukraine, Zelenskyy warned he would not negotiate with the Kremlin as long as Putin is in power.

On Wednesday, Putin declared martial law in those regions — Donetsk, Kherson, Luhansk and Zaporizhzhia. The move follows a string of embarrassing setbacks for Putin, including losses on the battlefield and struggles with his efforts to mobilize hundreds of thousands of more troops.

“I think it's another sign of Putin’s desperation,” Blinken said. “Just in the last few weeks, he's tried to mobilize more forces. He's gone through with this sham annexation of Ukrainian territory. Now he’s saying that he's declaring martial law in places that he claims have people who somehow want to be part of Russia. That speaks to his desperation.”

Blinken said the United States’ objective in the war is “simple.”

“It's to stand with the Ukrainians to make sure that their country remains independent and, ultimately, to have the strongest possible hand at the negotiating table if one emerges,” he said.

Meanwhile, Putin has increasingly threatened to use nuclear weapons. Blinken said the United States is watching Russia’s actions “very, very carefully” but has not seen any reason to change its own nuclear posture.

“We've been very clear with President Putin directly and privately about the severe consequences that would follow from any — any — use of a nuclear weapon,” Blinken said.

He did not elaborate on what those consequences might be.