"We are now deeply concerned by reports of military movements taken by the Russian Federation inside of Ukraine," Obama said on Friday. (Agencies)
Obama issued the statement at the White House after a Ukrainian official warned of a Russian "invasion" and said up to 2,000 Russian troops had arrived in the restive peninsula.
Obama called on Russia to respect the independence and territorial integrity of Ukraine
"Russia has a historic relationship with Ukraine, including cultural and economic ties, and a military facility in Crimea, but any violation of Ukraine’s sovereignty and territorial integrity would be deeply destabilising, which is not in the interest of Ukraine, Russia, or Europe," he said.
Obama said any such Russian move would represent a profound interference in matters that must be determined by the Ukrainian people.
"Just days after the world came to Russia for the Olympic Games, it would invite the condemnation of nations around the world. The United States will stand with the international community in affirming that there will be costs for any military intervention in Ukraine," said US President.
Obama said the events of the past several months remind of how difficult democracy can be in a country with deep divisions.
"But the Ukrainian people have also reminded us that human beings have a universal right to determine their own future. Right now, the situation remains very fluid," he added.
Obama said that Vice-President Joe Biden had spoken on Friday with the new Prime Minister of Ukraine Arseniy Yatsenyuk to offer Washington's support for his country's democratic future.
"I also commend the Ukrainian government’s restraint and its commitment to uphold its international obligations," he said.
Obama said over the last several days, US has been responding to events as they unfold in Ukraine.
"Throughout this crisis, we have been very clear about one fundamental principle: The Ukrainian people deserve the opportunity to determine their own future," he said.
"I also spoke several days ago with President Putin, and my administration has been in daily communication with Russian officials, and we've made clear that they can be part of an international community’s effort to support the stability and success of a united Ukraine going forward, which is not only in the interest of the people of Ukraine and the international community, but also in Russia’s interest," Obama stressed.
"We are now deeply concerned by reports of military movements taken by the Russian Federation inside of Ukraine," Obama said on Friday.