Speaking from the South Lawn of the White House, Obama warned that "If Russia continues on its current path, the cost on Russia will continue to grow."
The new sanctions target three of state-owned Moscow-based banks: Bank of Moscow; Russian Agricultural Bank; and VTB Bank OAO.
A senior U.S. administration official, commenting on the additional sanctions, said that the U.S. has now imposed sanctions against five of the six largest state-owned banks in Russia.
Obama's announcement coincides with an agreement by the European Union to impose new sanctions against Russia.
"In the financial sector, the EU is cutting off certain financing to state-owned banks in Russia. In the energy sector, the EU will stop exporting specific goods and technologies to Russia, which will make it more difficult for Russia to develop its oil resources over the long term. In the defense sector, the EU is prohibiting new arms imports and exports and is halting the export of sensitive technology to Russia's military users."
A senior U.S. administration official, speaking on background, described the EU sanctions as "strong. They are significant. They represent a new step for Europe, and one that we and the European have taken together."
Obama heralded the EU's unified response to Russia as "a reminder that the United States means what it says. We will rally the international community in standing up for the rights and freedom of people around the world."
Tuesday's announced sanctions are the latest in a series of economic steps taken to isolate Russia in response to its intervention in Ukraine. When a senior U.S. administration official was asked Tuesday about the end-game for this newest round of sanctions, and whether more are in the offing, he indicated that time will tell.
"Today's step is a very substantial move by the U.S. and we will want the impact of these sanctions to sink in to judge Russia's willingness to take the path" toward de-escalation.
"We been very clear about the conditions that Russia must take" for sanctions to be eased, he said. Those steps, also referred to by the White House as the "off-ramp" option, include:
1. Recognition of Ukrainian President Petro Poroshenko's government;
2. An end to providing weapons and arms to separatists in Ukraine;
3. Removal of Russian military forces along Ukraine's border;
4. Use of Russian influence over separatists in Ukraine to bring them into political dialogue with Poroshenko's government.
If Russia begins to take steps to de-escalate tensions, "we will continue to hold that door open," the official noted.
"If not, we have more sanction targets available to us."