President Barack Obama says that if Russia continues an aggressive path in Ukraine, the United States and other countries will, in his words, be "forced to apply costs" to Moscow.
Obama made his remarks after meeting with Ukraine's new prime minister, Arseniy Yatsenyuk, at the White House in a display of support for the fledgling government.
Obama referred to the Russian military presence in Ukraine's Crimean Peninsula and said the greatest threat facing Ukraine is to its territorial integrity.
Yatsenyuk said Ukraine will, quote, "never surrender" in a fight over its territory.
The Crimean regional government has scheduled a referendum Sunday on whether to separate from Ukraine and join the Russian federation.
Obama said he will stand with Ukraine in ensuring that its territorial integrity is maintained.