Washington is looking at a "broad range of options" for sanctions it could impose on Russia unless it defuses tensions in Ukraine, a senior US official said Monday.
"This is a step we are very prepared to move forward on," State Department spokeswoman Jen Psaki said, warning that the US administration is already examining sanctions on Russian individuals and institutions.
"I would say that the steps that we are taking are having an impact," she said, pointing as an example to an announcement from the G8, which symbolically called itself the G7, that it would skip preparatory meetings this week for a summit in Russia in June.
"If you look at the sharp decline of the Russian ruble, if you look at the Russian stock market today, those are just two examples," she said.
Psaki said there was no time-frame as yet for when the United States could impose sanctions, but added "we're looking at a broad range of options, whether that's individuals, whether that's institutions, whether that's officials, those are all under consideration."
Washington was working "in lockstep" with its European allies on the question of imposing sanctions on Moscow, as Russia appeared to tighten its grip on Ukraine's southern Crimea peninsula.
"We work closely with them as we look to take steps, whether that's sanctions, whether that's economic assistance, whether that's efforts to support the IMF, whether that's efforts to hold others accountable," Psaki told reporters on a phone conference call.
"We will keep them informed of what we're considering," she said.
US Secretary of State John Kerry said on Sunday that sanctions could be considered to try to rein in Russia's military intervention in Crimea.
And he further warned that Russia could be stripped of its membership of the prestigious Group of Eight most industrialized nations, saying its actions were incompatible with G8 principles.