Ukraine Says Russian Forces Focusing on Donetsk, LuhanskUkraine’s military said Tuesday that Russian forces are focusing on trying to take full control of the Donetsk and Luhansk regions, strategic areas in the eastern part of the country that would allow Russia to link with the Crimean Peninsula it seized eight years ago. The statement from the military’s General Staff, which also said Russian “missile and airstrikes on civilian targets throughout Ukraine do not stop,” came a day after Russia launched its long-expected assault in eastern Ukraine following a pullback from areas around Kyiv. "Now, we can already state that the Russian troops have begun the battle for the Donbas, for which they have been preparing for a long time,” Ukrainian President Volodymyr Zelenskyy said in a video address late Monday. He said a "significant part of the entire Russian army is now concentrated on this offensive." The Donbas region includes Luhansk and Donetsk, two provinces that are already partly held by Russian-backed separatists, along with the besieged port city of Mariupol to the south. Russia has demanded the remaining Ukrainian troops in Mariupol lay down their arms, including a fresh ultimatum with a Tuesday afternoon deadline. The Russian defense ministry said those who do give up would be “guaranteed survival.” Ukraine has rejected all demands to surrender the city. Russia also said Tuesday its forces struck more than 1,200 targets with missile and artillery strikes overnight, including dozens in eastern Ukraine. Pentagon spokesman John Kirby told reporters Monday that Russia has concentrated such strikes in the Donbas and areas to the south, particularly in Mariupol “where the preponderance of their strike activity has gone.” Kirby said Russia has been moving “artillery, rotary aviation, helicopter support, command and control enablers” to aid its Donbas efforts. Humanitarian officials have raised concerns about disruptions in getting supplies to people in areas that have seen some of the worst violence, including Mariupol, and to establish safe corridors for civilians to flee to safety. Ukrainian Deputy Prime Minister Iryna Vereshchuk said Tuesday there would be no humanitarian corridors active for a third consecutive day due to a lack of agreement with Russia. U.N. relief chief Martin Griffiths told reporters Monday that the two sides need to negotiate a meaningful cease-fire in order to facilitate getting help to civilians. “On the humanitarian side, we need to have much, much more willing acceptance, primarily of the Russian Federation, to allow convoys in and convoys out in these places of great need,” Griffiths said. “And we need in those places where the war has for the moment moved on to provide urgent emergency, if you like humanitarian assistance, to get people to be able to see their homes again and maybe reach them.” U.S. President Joe Biden is holding a video call with allies Tuesday to discuss what the White House called "our continued support for Ukraine and efforts to hold Russia accountable." Asked Monday if the Biden administration is considering more sanctions against Russia, White House press secretary Jen Psaki told reporters the United States will "continue to expand our sanctions targets and continue to take steps to both further tighten our sanctions to prevent evasion." Russian President Vladimir Putin contended Monday during a video call with economic officials that the sanctions imposed by the United States and its allies had failed. In Denmark, Prime Minister Mette Frederiksen said his country should move as quickly as possible to be independent of Russian gas supplies. Denmark will boost its production of natural gas for a limited time while also working to produce as much energy from renewable sources as it can, Frederiksen said. "We are convinced it's better to produce gas in the North Sea than buying it from Vladimir Putin," Frederiksen said. European Union members rely on Russian gas imports to meet about 40% of their needs. Denmark is not among EU countries most dependent on Russia for energy. Zelenskyy has urged EU countries to halt their Russian energy imports and for Western nations to sanction the Russian oil industry in order to pressure Putin to halt the invasion. While some leaders have expressed a willingness to reduce or end the imports, they have also cited fears of the effects that a quick cutoff would have on their own economies. Russia initially described its aims as disarming Ukraine and defeating nationalists there. Kyiv and its Western allies say those are bogus justifications for an unprovoked war of aggression that has driven a quarter of Ukraine's 44 million people from their homes. Some information for this report came from The Associated Press, Reuters and Agence France-Presse.