There could be more sanctions, too.

But any moves made must be strong, experts agreed.

Putin must be made to understand "his actions are not increasing Russia power," Mansoor said, "but actually bringing U.S. power closer to Russia."

Because, right now, what's happening in Ukraine Thursday "shows that Putin's desires in that region have not yet been satisfied," Mansoor said, "and he's willing to risk further sanctions and further war."