"We have helped in many ways to create the problems that exist there. And to leave them alone in the manner that we are leaving them alone to me is just unconscionable," Sen. Bob Corker, the committee's senior Republican member, said on NBC television’s ‘Meet the Press’.

"I don't think Putin really believes we are going to punish them in that way," he said.

Democratic Senator Chris Murphy, a member of the same committee, said, "I think the time is now to rapidly ratchet up our sanctions, whether it is on Russian petrochemical companies or on Russian banks."

"If Russia does get away with this, I do think that there is a potential that a NATO ally is next. And, yes, there will be economic pain to Europe. But it is time for them to lead as well," he added.

President Barack Obama has said that his administration is prepared to take further action against Russia if diplomatic efforts to destabilize the conflict fail.

Vice President Joe Biden plans to be in Kiev, the Ukrainian capital, on Monday and Tuesday to meet with government leaders and democracy advocates.

Defence Secretary Chuck Hagel said last week that US is looking for ways to reassure its NATO allies of its strong commitment to collective defence.

The Pentagon's press secretary, Rear Adm. John Kirby, has said the American officials are considering a range of additional measures to bolster air, maritime and ground readiness in Europe.

A Western official said yesterday that US is considering deploying about 150 soldiers for military exercises to begin in Poland and Estonia.

(Agencies)

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