President Barack Obama on Thursday ordered the freezing of U.S. assets and a ban on travel into the United States of those involved in threatening the sovereignty and territorial integrity of Ukraine.
Obama signed an executive order aimed at punishing those Russians and Ukrainians responsible for a Russian incursion into the Crimean region of southern Ukraine, a crisis that has raised old-style Cold War tensions.
The order, the White House said in a statement, is "a flexible tool that will allow us to sanction those who are most directly involved in destabilizing Ukraine, including the military intervention in Crimea, and does not preclude further steps should the situation deteriorate."
"At the same time, as the president has said, we seek to work with all parties to achieve a diplomatic solution that de-escalates the situation and restores Ukraine's sovereignty," the statement said. "We call on Russia to take the opportunity before it to resolve this crisis through direct and immediate dialogue with the Government of Ukraine."
In addition, the State Department is putting in place visa restrictions on a number of officials and individuals.
(Read more: Vitali Klitschko: Putin worried over Ukraine)
The new restrictions were announced in Washington as Secretary of State John Kerry headed into a meeting with Russian Foreign Minister Sergey Lavrov in Rome on the sidelines of a diplomatic forum about Libya.
A senior administration official said the restrictions are aimed at Russians and Ukrainians in the strategic Crimea region. Crimea is a peninsula that hosts a major Russian navy base and is historically and culturally a stronghold of Russia.
Local government officials in Crimea are now seeking to separate from Ukraine, and on Thursday set a March 16 date for a referendum vote on whether the region should become part of Russia.
—By Reuters and The Associated Press.