"We are not going to be getting into a military excursion in Ukraine," Obama told San Diego NBC affiliate KNSD.
"What we are going to do is mobilize all of our diplomatic resources to make sure that we've got a strong international coalition that sends a clear message," Obama added. “Ukraine should decide their own destiny. Russia right now is violating international law and the sovereignty of another country. Might doesn’t make right.”
Obama vowed to continue to “ratchet up the pressure on Russia.”
“Even the Ukrainians would acknowledge that for us to engage Russia militarily would not be appropriate and would not be good for Ukraine,” he said.
The interview was one of several the president conducted with local news media outlets Tuesday afternoon at the White House.
The president's remarks come a day after Russian President Vladimir Putin signed a treaty annexing Crimea. The region was seized by Russian military troops after Moscow-backed former Ukrainian President Viktor Yanukovych was booted from power. On Sunday, under Russian control, voters in a referendum approved a measure to secede from Ukraine.
The U.S. has said it will not accept the referendum and has called on Russia to draw down its military troops and negotiate with the interim government in Kiev. But Putin has refused to back down even under the threat of sanctions, saying that he is only protecting the safety of ethnic Russians in the region.
Russian troops began seizing control of Ukrainian military bases in the region.
White House press secretary Jay Carney warned that Moscow would be "directly responsible" for any casualties, after one Ukrainian officer was killed in a clash.
Earlier this week, the Obama administration instituted sanctions against a number of Russian and Ukrainian officials and has promised further "costs."
This story was published at 5:56 p.m. and has been updated.