U.S. President Barack Obama on Thursday announced new sanctions against senior Russian officials and a bank in a move to "impose additional costs" on Russia."Based on the executive order that I signed in response to Russia's initial intervention in Ukraine, we're imposing sanctions on more senior officials of the Russian government," Obama said at the White House.Washington is also imposing sanctions on a number of other individuals who provide material support to the Russian leadership, as well as a bank that provides material support to these individuals, Obama said, adding that the steps are part of the U.S. response to Russia's moves in Crimea.The new punitive measures came following a first round of sanctions Obama announced on Monday against 11 Russian and Ukrainian officials. A senior U.S. official told reporters on Thursday that the latest measures cover 20 Russian individuals, who will have their assets in the United States frozen and be barred from doing business in relation to the United States.Bank Rossiya, the bank subject to the sanction, will be "frozen out of the dollar," said the official, adding that the bank provides services to many of the senior Russian government officials being sanctioned. It is the 17th largest bank in Russia with about 10 billion U.S. dollars in assets.In addition, Obama said he had signed a new executive order on Thursday to impose sanctions on key sectors of the Russian economy.The new sanctions would not only have a significant impact on the Russian economy, but could also be "disruptive" to the global economy, Obama said."Russia must know that further escalation will only isolate it further from the international community," Obama added.On Tuesday, Russian President Vladimir Putin signed a treaty with the leaders of Crimea to accept the Republic of Crimea and the city of Sevastopol as part of the Russian territory. The agreement follows Monday's decision by the Crimean parliament to declare independence from Ukraine after official results from the referendum on March 16 showed 96.77 percent of Crimean voters chose to join Russia.On Thursday, Obama warned Russia not to take further military actions in southern and eastern Ukraine, saying that the U.S. has been working closely with its European partners to "develop more severe actions" should Russia continue to escalate the situation.He urged Congress and the IMF to move more swiftly in providing economic aid to Ukraine in order to stabilize its economy and meet the basic needs of the Ukrainian people."Expressions of support are not enough. We need action," Obama said.Reinforcing a message U.S. Vice President Biden had sent in his visit to Poland and the Baltic states this week, Obama said U.S. support for its NATO allies is "unwavering"."We've already increased our support for our Eastern European allies and we will continue to strengthen NATO's collective defense, and we will step up our cooperation with Europe on economic and energy issues as well," he said.While imposing tough sanctions on Russia, Obama emphasized that diplomacy between the United States and Russia continues and diplomacy remains a solution."Russia still has a different path available, one that de- escalates the situation and one that involves Russia pursuing a diplomatic solution with the government in Kiev, with the support of the international community," he added.