Washington – Ukrainian President Volodymyr Zelensky said Sunday he did not believe Russian President Vladimir Putin was bluffing with his threats to use nuclear weapons and called on Ukraine’s allies to keep up pressure on Putin to rein him in.

“Maybe it was a bluff yesterday. Now it can be a reality,” said Zelensky in an interview with “Face the Nation”. “He wants to scare the whole world. These are the first steps of his nuclear blackmail. I don’t think he’s bluffing. I think the world is holding him back and holding back this threat. We have to keep putting pressure on him and not let him continue.”

Putin last week threatened to use nuclear weapons when he announced a partial mobilization of his military reserves, forcing Russian men of military age to leave the country to avoid fighting in Ukraine. Putin’s call-up of the military reserves came just before people in Russian-occupied regions of Ukraine began voting to become part of Russia, a process condemned by the West.

President Biden said on Friday that the referendums were a “false pretext for trying to annex part of Ukraine”, while Zelensky warned that the annexation would make it “impossible” for diplomatic talks with Putin to continue.

“He knows it well. I spoke about it publicly,” Zelensky said about Putin. “I think this is a very dangerous signal from President Putin, telling us that Putin is not going to end this war. That’s what’s happening.”

Ukraine’s president called on the US and European allies to continue imposing sanctions against Putin, but also called on the Biden administration to recognize Russia as a state sponsor of terrorism.

“I understand that there will be consequences. These consequences will make diplomatic negotiations impossible,” said Zelensky. “However, they are terrorists and we cannot allow them to do this out of fear. They will not give up. We need to continue the pressure.”

However, the White House said earlier this month that Mr Biden would not designate Russia as a state sponsor of terrorism because of “unintended consequences” for Ukraine and the world.

Zelensky also said that it is vital for Ukraine to continue obtaining high mobility missile and artillery systems (HIMARS), artillery and air defense systems. The Biden administration has asked Congress to approve another $12 billion for Ukraine, but lawmakers have yet to act.

“Why do we do this? We need security to attract our Ukrainians to return home,” he said. “If it’s safe, they’ll come, settle, work here and pay taxes, and then we won’t have a $5 billion budget deficit. So it will be positive for everyone.”

Zelensky said the coming winter months will be a challenge for Ukraine, and he expects Russia to target his country’s power grid.

“But we are not afraid of it,” he said. “We will fight and we will not give up. It is very important that they do not make other countries, the United States of America and Europe suffer. Now we are suffering. We are fighting and giving our lives for the future of democracy and an open world.”

Zelensky also predicted that he became a target of Putin not only because he resisted Russia and its constant invasion, but also as the country’s leader.

“He is doing everything he can to destabilize our country so that we are weaker,” he said. “And for that he wants to divide us, of course I’m one of the targets, of course it goes without saying.”