Russia will face complete isolation if it invades Ukraine, U.S. Secretary of State John Kerry has said.

"[U.S.] President [Barack Obama] has made it clear that there are many different options, but that would be taken, needless to say, as not just a violation of all notions of international law, but an exceedingly dangerous action," Kerry said at a press conference on Tuesday, when asked what the United States is going to do if Russia invades Ukraine.

"It would wind up with, you know, the most severe possible kinds of isolation and sanctions possible. And Germany, France, other countries in Europe, would clearly join into that in ways that would have a profound, profound impact on the Russian economy," he said.

Kerry said that the United States was already helping Ukraine in the crisis situation.

"We are working very, very closely already providing advice and materials to Ukraine, as well as other countries that are doing the same thing. And we are working very, very hard to see if we can't find the political key to be able to provide redress for the grievances that President Putin keeps talking about through the political process," he said.

He said that the United States realizes that Russia has its own interests and historic connections in Ukraine.

"What Ukraine is looking for is simply respect for its sovereignty, and hopefully the political process that is unfolding now can address the concerns in a way that will strengthen that sovereignty," Kerry said, adding that the EU and the U.S. want this policy to be implemented.