Russia's invasion of Ukraine will be at the center of President Biden's address to the U.N. General Assembly on Wednesday, as the U.S. warns Russia is trying to annex more Ukrainian land.

In an interview with 60 Minutes set to air Sunday night, President Joe Biden says that his clear advice to Russian President Vladimir Putin if he is "considering using chemical or tactical nuclear weapons" in Ukraine, would be this: "Don't. Don't. Don't."The question was asked by news correspondent Scott Pelley, who described a current state of affairs in which Putin, after nearly 9 months of protracted war and recent gains by a Ukrainian counter-offensive, is feeling "embarrassed and pushed into a corner."Asked what he would do in response to any kind of nuclear strike, Biden said, "You think I would tell you if I knew exactly what it would be? Of course I'm not going to tell you." But, he added, "It'll be consequential."Such a move, said Biden, "would change the face of war unlike anything since World War II."The comments from Biden come just days after a new report from the Costs of War Project at Brown University's Watson Institute for International and Public Affairs warned that a continued buildup of conventional military weapons by the U.S. and other European allies in Ukraine increases the risk of a nuclear confrontation."Russian aggression in Ukraine requires an international response. However, it does not justify increased U.S. military budgets, which could ultimately escalate tensions with Russia and once again lead us down a dangerous path," said Costs of War Project co-director Stephanie Savell.Instead of increasing the flow of weapons into Ukraine, the paper advises "de-escalatory approaches" to end the war unleashed by Putin's invasion. Such measures should include "direct talks, reviving the arms control agenda, and pursuing military confidence-building measures between NATO countries and Russia."In a series of tweets late last week, Beatrice Fihn, executive director of the International Campaign to Abolish Nuclear Weapons (ICAN), winner of the 2017 Nobel Peace Prize, said she was deeply troubled by the way journalists and analysts throw around the term "tactical nuclear weapons" without putting them in their proper context."Whether or not the risk is high or low, when we describe what Russian use of nuclear weapons would do in Ukraine, we have to mention that hundreds of thousands of Ukrainians would die," Fihn tweeted on Thursday. "Even if it stopped with one bomb, it would be an unprecedented humanitarian catastrophe.""This to me," she added, "is one of the main problems of many nuclear analysts. It is detached from reality and real people, and only talks about abstract strategy and theory. It's how we desensitize decision-makers and the public and make the use of nuclear weapons sound normal and acceptable."

President issues vow as tensions with China rise.

President Joe Biden said it was "much too early" to decide whether he was going to run for re-election.

President Biden’s approval rating has climbed to 42 percent, and the number of Americans who believe the country is on the right track has doubled but remains low.