President Obama said Thursday that a proposed referendum for Crimea to join Russia violates Ukraine's constitution and international law.
Speaking from the White House briefing room, Obama said any discussions about Ukraine's borders have to include Ukraine.
"In 2014, we are well beyond the days when borders can be redrawn over the heads of democratic leaders," Obama said.
His remarks came as the crisis in Ukraine intensified and the administration sought to rachet up pressure on Russia, imposing sanctions and visa restrictions on Russian officials it deems responsible for the intervention into Crimea.
Obama said an executive order he signed Thursday authorizes sanctions on "individuals and entities responsible for violating the sovereignty and territorial integrity of Ukraine, or for stealing the assets of the Ukrainian people."
And he said the State Department has put in place restrictions on the travel of certain individuals and officials -- moves he said "continue our efforts to impose a cost on Russia and those responsible for the situation in Crimea."
He said the measures can be changed, "based on Russia’s actions."
He said European allies are also imposing sanctions, saying he's "confident that we are moving forward together, united in our determination to oppose actions that violate international law and to support the government and people of Ukraine."
Still, Obama said there's a "path of de-escalation" and an exit for Russia "that respects the interests of the Russian Federation, as well as the Ukrainian people," including letting international monitors into all of Ukraine and engaging in talks between Russia and Ukraine.
"Russia would maintain its basing rights in Crimea, provided that it abides by its agreements and respects Ukraine’s sovereignty and territorial integrity," Obama said. "But if this violation of international law continues, the resolve of the United States, and our allies and the international community will remain firm."
He noted "a lot of talk in Congress about these issues" and called on lawmakers to support the International Monetary Foundation's efforts in Ukraine.
The White House earlier said it will block Russian officials from the U.S. and that Obama has signed an executive order that allows sanctions against "individuals and entities responsible for activities undermining democratic processes or institutions in Ukraine."
In a statement, the White House said Obama has made clear that the U.S. is "pursuing and reviewing a wide range of options in response to Russia’s ongoing violation of Ukraine’s sovereignty and territorial integrity – actions that constitute a threat to peace and security and a breach of international law, including Russia’s obligations under the UN Charter and of its 1997 military basing agreement with Ukraine, and that are inconsistent with the 1994 Budapest Memorandum and the Helsinki Final Act."
As part of that review, the State Department today is putting in place visa restrictions on a "number of officials and individuals," the White House said, "reflecting a policy decision to deny visas to those responsible for or complicit in threatening the sovereignty and territorial integrity of Ukraine."
The department had earlier moved to deny visas to those involved in human rights abuses related to political oppression in Ukraine. In addition, Obama signed an executive order authorizing sanctions "on individuals and entities responsible for activities undermining democratic processes or institutions in Ukraine; threatening the peace, security, stability, sovereignty, or territorial integrity of Ukraine; contributing to the misappropriation of state assets of Ukraine; or purporting to assert governmental authority over any part of Ukraine without authorization from the Ukrainian government in Kyiv."
The White House called the order a "flexible tool" that would allow it 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."
The U.S. has already suspended bilateral discussions with Russia on trade and investment and put on hold U.S.-Russia military-to-military engagement, including exercises, bilateral meetings, port visits, and planning conferences.
Its also suspended preparation for the scheduled G-8 Summit in Sochi in June and said Thursday that "depending on how the situation develops, the United States is prepared to consider additional steps and sanctions as necessary."
And it said it's hoping for a diplomatic resolution -- though talks Wednesday failed to achieve an agreement.
" We call on Russia to take the opportunity before it to resolve this crisis through direct and immediate dialogue with the government of Ukraine," the statement said, adding it will honor NATO defense commitments and look at measures, including "the provision of additional support to NATO's Baltic Air Policing mission and our aviation detachment in Poland."