Washington — Ukrainian President Volodymyr Zelenskyy said that world leaders need to put "more pressure," including sanctions, on Russian President Vladimir Putin to bring him to the negotiating table as Zelenskyy seeks to end the war that has stretched on for more than four years. 

Zelenskyy indicated battlefield gains over the next six months could strengthen Ukraine's hand in future peace talks, echoing remarks made last week by Brigadier General Andriy Biletsky, a top Ukrainian commander. 

"Before the winter, we need to find a way, diplomatic way, to sit and to speak," Zelenskyy said in an exclusive interview for "Face the Nation with Margaret Brennan." The interview was taped on May 29 and aired Sunday. 

The Institute for the Study of War, a nonpartisan think tank that tracks the battlefield, concluded earlier this month that Ukrainian forces may have an edge. 

"Russian forces' rates of advances are stagnating while Ukrainian forces are employing novel tactics and operational concepts in efforts to break out of positional warfare," the ISW said in an analysis published May 25. "It remains too early to tell whether Ukrainian forces will successfully restore maneuver to the battlefield, however.

Zelenskyy again pleaded for additional U.S. support. 

On Monday, he sent a letter to President Trump and Congress requesting additional Patriot ballistic missile interceptors, a request that took on additional urgency after Russia carried out a massive attack on Kyiv, launching dozens of cruise and ballistic missiles in what was the largest aerial assault since the war began in 2022. 

"We need to increase the production," Zelenskyy told Brennan about the supply of PATRIOT missiles. "Sixty, 65 missiles per month for today's challenges, it's nothing."

The White House did not respond to CBS' request for comment on the letter. 

Defense Secretary Pete Hegseth was asked about Ukraine's request earlier this week. 

"Listen, we're changing the way we make all those types of important munitions to ensure that our companies are delivering not just a little bit more, but a lot, a bit more, across the spectrum," he told reporters at a defense forum in Singapore. "Where we can help Ukraine, we have, where we can enable Europe to do more, we have, and I'm encouraged by the European commitment. You look at the amount of money that's been spent, Europe has stepped up, and Ukraine has been just as, if not more effective in the process, so we want them to be able to defend, and we'll find a way to make sure we can help them." 

ISW's May 25 analysis found that time may be of the essence. 

"Ukraine likely has a unique and time-constrained opportunity to exploit its current initiative while Russian forces remain vulnerable," it found. "Ukraine's partners should expand their support to these Ukrainian efforts at a moment when Russia is reeling from both battlefield setbacks and Ukraine's deep strike campaign with the aim of forcing Russian President Vladimir Putin to reevaluate his approach to this conflict." 

Meanwhile, U.S. Secretary of State Marco Rubio appeared to acknowledge earlier this month that talks to end the war have stalled, though the U.S. is prepared to reengage if there's an opportunity for fruitful negotiation. Asked whether Russia can ever come to a negotiated end to the war, Zelenskyy said "Yes, of course." He pointed to a number of possible tracks, including the trilateral talks with the U.S. earlier this year, while offering to sit down in multiple formats to negotiate an end to the war. 

"It was a priority then, United States be open, and we have to be open, between us, we are partners," Zelenskyy said of the trilateral talks. "United States moved and shift their focus on the Middle East, and because of this, I think Middle East is a priority. That's why we have some pauses in our diplomatic negotiations."

Zelenskyy said "we count on" negotiators including Rubio, Steve Witkoff and Jared Kushner, coming to Kyiv. The Ukrainian president said he's hopeful that they will make the trip in two weeks. According to a White House official, a visit has been discussed, but not yet scheduled.

Zelenskyy emphasized that "I think that we need to see [an] American negotiation group in Ukraine."

"They've never been here. I think it's important, not [only] for us," he said. "It's useful for them to understand, to see, to see people, that their life is going on, but we want to stop this war."

The Ukrainian president also pointed to a possible European track to bring an end to the war through negotiations, while noting that "I will always be on the side that it can't be just United States track or European."

"The most strong position is when Ukraine, Russia, America- United States, and Europe, I think that this is the most strong, powerful negotiation format," he said. "But, we have what we have. Now, Europe tries to find their way how to push Russia to the peace."

The third option, Zelenskyy said, is bilateral talks with Russia. He said "I'm ready to meet with Putin if he will be ready," emphasizing that additional pressure on the Russian president could bring him to the table. 

"I think we need more sanctions. I think we need more pressure," Zelenskyy said. "More sanctions, more pressure, they will be ready for the dialogue."

Zelenskyy said Russia is losing up to 35,000 soldiers each month, arguing "they are on the way to the big crisis with the people."

"I think all these things will push them to the dialogue," he said. 

Zelenskyy emphasized the need for additional sanctions on Russia to increase pressure on Putin. Russia has faced tight sanctions since it launched the full-scale invasion of Ukraine in 2022. But it's seen a temporary reprieve on the purchasing of some Russian oil amid the war with Iran, as the world grapples with high oil prices. Treasury Secretary Scott Bessent, asked by CBS News last week whether the U.S. is considering putting sanctions on Russia, said "this administration has put the hardest sanctions on Russia of any country."

Zelenskyy said "I hope that the United States will do it."

On a possible drone deal with the U.S., Zelenskyy said "I hope that we are on the way."

"But we have already drone deals with some Middle East countries, and we have already drone deals with some European countries. Now we're preparing the big drone deal with EU, and I hope that we will have such decisions with American partners," he said. "I count on it."

Zelenskyy outlined that U.S. tech companies "have a lot of different interesting AI technologies what we don't have, and we have a lot of things what they don't have, because our experience on the battlefield."

"I think this cooperation can be huge and the most powerful in the world," he said. "So we need to negotiate already, not to speak about it, just to make steps, and to do it as quick as possible."

He added, "we need President Trump to say yes."