President Barack Obama made new comments on the situation in Ukraine on Thursday, announcing the U.S. is moving "to impose additional costs on Russia."

Obama said he signed a new executive order Thursday that allows the U.S. "to impose sanctions on key sectors of the Russian economy."

"Russia must know that further escalation will only isolate it further from the international community," Obama said.

Obama urged Congress to pass an aid package to support Ukrainians pursuing reforms.

"Expressions of support are not enough," Obama said. "We need action."

Obama did note that "diplomacy between the United States and Russia continues."

"We've emphasized that Russia has a different path available," Obama said.

"Mr. Putin should know that the Ukrainians shouldn't have to choose between the west and Russia," he added.

UPDATE -- 11:45 a.m.:The AP reports Russia has imposed an entry ban on American lawmakers and officials in retaliation for the U.S. sanctions.