Putin Orders Nuclear Deterrent Forces on High AlertUkraine has agreed to hold talks with Russia at the Belarus border, as Russian President Vladimir Putin orders Russian nuclear deterrent forces on high alert. With tensions with the West soaring over Russia’s invasion of Ukraine, Putin told the Russian defense minister to put nuclear forces in a “special regime of combat duty” Sunday. He told his officials that leading NATO powers had made “aggressive statements” and imposed hard-hitting financial sanctions against Russia. White House press secretary Jenn Psaki told ABC News Sunday Putin was continuing his pattern of “manufacturing threats that don’t exist in order to justify further aggression.” “At no point has Russia been under threat from NATO, has Russia been under threat from Ukraine,” she said. Ukrainian President Volodymyr Zelenskyy agreed to send a delegation to the Belarus border to start peace talks with Russia without preconditions. "We agreed that the Ukrainian delegation would meet with the Russian delegation without preconditions on the Ukrainian-Belarusian border, near the Pripyat River," his office said in a statement. Earlier, Zelenskyy had said he would enter peace talks with Russia but ruled out meeting inside Belarus because Russia had used it to launch its attacks on Ukraine. The Ukrainian ambassador to the United States, Oksana Markarova, stressed that the government was ready for peace talks but not ready to surrender, adding that the Ukrainian government had filed suit against Russia at the International Criminal Court for war crimes in Ukraine. “They’re using missiles and heavy artillery and troops around the country to essentially target the civilian infrastructure, hospitals; we now see the kindergartens. I mean, nothing is off limits to them,” Markarova told ABC. Russian troops continued to battle Ukrainian defense forces and citizen soldiers for control of Kyiv, the capital, and other cities Sunday, the fourth day of Russia’s invasion. Russian troops who entered Kharkiv, Ukraine’s second-largest city that sits some 40 kilometers from the Russian border, were met with heavy resistance. Early Sunday, the Ukrainian president's office reported an explosion there and said Russian forces had blown up a gas pipeline. There are also reports of shelling in the eastern Ukrainian city of Donetsk, which has been held by Russia-backed separatists since 2014. Western allies are responding to Zelenskyy’s call for help. German Chancellor Olaf Scholz said Saturday his country will send Ukraine 1,000 anti-tank weapons and 500 Stinger surface-to-air missiles “as quickly as possible,” and the French presidential office said France will send defensive weapons and fuel. “The anti-war coalition is working,” Zelenskyy tweeted. Ukraine’s foreign minister, meanwhile, has posted a notice on Twitter inviting foreign nationals to join in Ukraine's battle against Russia. Lines of vehicles clogged Ukraine’s borders as refugees continued to leave the country. The United Nations’ refugee agency said Sunday more than 200,000 had fled, half of them to Poland, and up to 4 million could flee if the situation worsens. U.S. sees ‘viable Ukrainian resistance’ “We continue to believe, based on what we have observed, that this resistance is greater than what the Russians expected … particularly in the north parts of Ukraine,” a U.S. Defense Department official told reporters Saturday. The official spoke on condition of anonymity in order to discuss intelligence. The official said Russian forces had unleashed a barrage of more than 200 ballistic and cruise missiles since the invasion began, most of them targeting the Ukrainian military. "They're meeting more resistance than they expected," the U.S. official said. Photo Gallery: Russian claims Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov claimed Saturday that since the start of Russia’s attack, its military had hit 821 Ukrainian military facilities, 87 tanks and other targets. Western officials cautioned that the situation was fluid and noted that things could change rapidly. They now estimate that half of the 190,000 Russian troops along the Ukrainian border had entered the fighting. At least 198 Ukrainians have been killed in the invasion, including three children, according to Russia’s Interfax news agency, which cited Ukraine’s Health Ministry. It was unclear whether the figure included only civilian deaths. Ukraine said more than 1,000 Russian soldiers had been killed, while Russia did not disclose casualty figures. Small anti-war protests continued in several Russian cities, including Moscow and St. Petersburg, and the Russian independent human rights media project OVD-Info reported that more than 489 people had been detained. National Security Correspondent Jeff Seldin, VOA Refugee Correspondent Heather Murdock in Kyiv, Jamie Dettmer in Lviv, Pentagon Correspondent Carla Babb, Senior Diplomatic Correspondent Cindy Saine and VOA’s Wayne Lee contributed to this report. Also some information in this report came from Reuters and The Associated Press.