Has Russia anything to fear from US sanctions tool kit?

President Obama has made long calls to President Putin to discuss Ukraine

The White House has said the US will "impose a cost" on Russia for its actions in Ukraine, but how much pain can the US inflict through diplomatic, political and economic means?

Several analysts weighed in on the options available to the US, from those the country has already taken to those that would take months or years to enact. Mark Katz, professor of government and politics at Virginia's George Mason University, then rated these options based on how devastating they might be to Russia and its President, Vladimir Putin.

Freezing assets

President Barack Obama has already signed an executive order to freeze the US-held assets of those responsible for undermining democracy in Ukraine. A black list is still being compiled, but it's likely to include Russia's wealthiest.

Pain Index (out of 10):9 "Asset freezes on the Russian elite's holdings in the West would be very painful," says Katz, who notes that Mr Putin is already calling on those with assets in the US to move them before the freeze can be put into effect.

Restricting travel

The state department is cancelling or rejecting visas of Russian officials who it says have contributed to Ukraine's instability. But consider it a warning shot, says Stephen Larrabee, distinguished chair in European Securities at the Rand Corporation.

"It is to show some sort of determination" on the part of the US, he says. "It could hurt the people that are sanctioned, but that's only a very few people." Still it has the power to cause disproportionate pain, especially if Europe joins in.

Pain Index: 8 "Moscow is especially sensitive to visa bans affecting the elite, though not so sensitive that it would change policy on Crimea," says Katz.

Isolating Russia via the G8

Secretary of State John Kerry has suggested kicking Russia out of the G8, the powerful group of nations and one of the most exclusive clubs in the world.

While outright expulsion isn't yet on the table, the US and the other nations have already pulled out of preparations for an upcoming G8 summit due to be held in Sochi, Russia, in June, and could boycott the event. But Russia may be willing to sacrifice the G8 in the name of a larger prize.

"It's something that matters, but at the end of the day it's a cost they are willing to live with if they can get what they want in Crimea," says Jeff Mankoff, deputy director and fellow with the Center for Strategic and International Studies Russia and Eurasia programme.

Pain Index: 1 for skipping the G8 talks, but 5 for kicking out Russia entirely. "This move would suggest that Russia under Putin is not a civilised state," says Katz.

Ending military exercises

The US already announced the cancellation of a joint military exercise between Russia, the US and Norway, but experts say it's another example of how limited America's options are.

"We're using most of our cards right now. We suspended military ties for the time being," says Larabee. "But there isn't a lot that we can easily do that would really hurt Russia."

Pain Index: 2 A powerful snub, but "the Russian military may not be eager for these anyway," says Katz.

Enabling a Russian gas boycott

Exporting natural gas to Europe is big money for Russia - a fifth of its total earnings, some $100bn (£60bn) a year, says Anders Aslund, a senior fellow at the Peterson Institute. If Europe stopped buying, it could introduce massive instability to the already weakening Russian economy.

It would be painful for Europe to wean itself off that gas. One way to soften that blow is for the US to provide some of the shale gas it now has in abundance.

At present the US offers a limited number of permits to export natural gas. So far, the White House says they have no plans to change the current energy policy - and putting the plan in place would take time and sacrifice for all parties involved. "It's not something you could just switch overnight," says Aslund.

Pain Index: 10 "If Western countries greatly curtailed oil and gas purchases from Russia, this would have a sharp negative effect on the economy of Russia," says Katz. But he adds that it would also have negative effects on the West.