The White House on Wednesday said that the U.S. has prepared new sanctions against Russia amid growing concerns over Ukraine's territorial sovereignty.

"It is accurate to say we have additional sanctions prepared and we will impose them as appropriate," White House press secretary Jay Carney told reporters aboard Air Force One en route to Pennsylvania with President Obama.

Carney, though, declined to share what those new sanctions would entail. It is also unclear when -- or if -- the administration would impose them.

The announcement comes as Ukraine’s military conducts a military operation to retake buildings and areas seized by pro-Russian nationalist groups in the east of the country. The Russian groups are calling for Moscow to protect them and urging secession from Ukraine.

Russian military forces have massed on the border, and while the Kremlin insists that it is not planning an invasion of its neighbor, the Obama administration has accused Moscow of working to destabilize Ukraine.

U.S., Ukrainian, Russian and European Union officials will meet in Geneva on Thursday to discuss the crisis, but Russian President Vladimir Putin has rejected prior calls from the west to pull back his military forces and urge the pro-Russian separatist groups to stand down.

The State Department on Wednesday unveiled a list of demands for Russia to destabilize the situation and also stressed that additional sanctions had been “prepared.”

Prior rounds of U.S. sanctions have targeted individuals found to be undermining democracy and Ukraine's sovereignty, a key Russian bank used by Putin's allies and an oil company based in the disputed Crimean region.