Russia assures US it won't invade Ukraine: Pentagon

US warned Russia that continued aggression would isolate the country further

Russia has assured America that it will not invade Ukraine, with the US warning that continued aggression would isolate the country further and result in more "diplomatic and economic pressure".

US Secretary of Defense Chuck Hagel, who made a call to his Russian counterpart Sergei Shoygu yesterday, also "emphasised that any diplomatic engagement must include the government of Ukraine".

"Hagel repeated his call for an end to Russia's destabilising influence inside Ukraine and warned that continued aggression would further isolate Russia and result in more diplomatic and economic pressure," Pentagon Press Secretary, Rear Admiral John Kirby, said.

According to Kirby, the two leaders discussed a wide range of issues related to the situation in Ukraine and "Shoygu reiterated his assurance that Russian forces would not invade Ukraine. Hagel emphasised how dangerous the situation remains and expressed his desire to find a responsible way forward."

During the call, Hagel requested clarification of Russia's intentions in Eastern Ukraine.

"Hagel noted that implementation of the agreement made on April 17 in Geneva would represent progress," Kirby said.

"Regarding recent actions by Ukrainian security forces, Hagel reiterated the right of the Government of Ukraine to preserve law and order within its own borders.

"He went on to ask his Russian counterpart for Russia's assistance in securing the release of the seven inspectors from the Organisation for Security and Cooperation in Europe currently being held in Eastern Ukraine, Kirby said.

Earlier in the day, Senators John McCain and Lindsey Graham said the Obama Administration's latest round of sanctions is "days late and dollars short".

"While a unified US and European response to Russia's aggression is ideal, the current policy has become a reduction to the lowest common denominator," they said.

"If we are now forced to choose between alliance unity or meaningful action, we must choose action, and America must lead it," the Senators said.

McCain and Graham said, the US needs to correct the disturbing mismatch between Russia's actions and our weak response to it.

"We need to expand sanctions to major Russian banks, energy companies, and sectors of its economy, such as the arms and mining industries, which serve as instruments of Putin's foreign policy," they said.