The assurance was given by Russian Defense Minister Sergei Shoygu, according to a statement released by the U.S. Defense Department.

　　"Secretary of Defense (Chuck) Hagel spoke today by phone with Russian Minister of Defense Sergei Shoigu (and) Shoigu reiterated his assurance that Russian forces would not invade Ukraine," Pentagon spokesman John Kirby said in the statement.

　　The two officials discussed a wide range of issues related to the situation in Ukraine, with Hagel requesting clarification of Russia's intentions in Eastern Ukraine, said Kirby.

　　Hagel emphasized in the phone call "how dangerous the situation remains and expressed his desire to find a responsible way forward, " and that Ukraine must be included in diplomatic talks, according to Kirby.

　　Tensions are continuing unabated in eastern Ukraine, where pro- Russia militants are engaged in conflicts with government troops and detaining eight military observers from the Organization for Security and Cooperation in Europe in Slovyansk, Ukraine, Friday before freeing one of them Sunday. Mayor Gennady Kernes of Kharkiv, also in Ukraine, was shot and seriously wounded Monday.

　　Hagel also asked Russia's help in securing the release of the other seven observers from the Organization for Security and Cooperation in Europe currently being held in eastern Ukraine.

　　The White House on Monday announced fresh sanctions on Russia, targeting seven government officials and 17 companies linked to the inner circle of President Vladimir Putin.

　　The EU is also expected to move against Russia as the leaders of the Group of Seven industrialized nations and the bloc issued a joint statement Friday saying they had agreed to "move swiftly" to impose more sanctions on Russia in response to its inaction in helping to ease growing tension in eastern Ukraine.