The U.S. Defense Secretary Chuck Hagel said here Wednesday that the U.S. plans to expand military cooperation with Poland and Baltic states to show " support" for its allies amid crisis in Ukraine.

"This morning the Defense Department is pursuing measures to support our allies," including expanded aviation training in Poland and increasing the U.S. role in NATO's air policing mission over Baltic countries, Hagel told lawmakers.

"This is a time for all of us to stand with the Ukrainian people in support of their territorial integrity and their sovereignty," Hagel said at a hearing of the Senate Armed Services Committee.

Hagel said over the past few days he and Chairman of the Joint Chiefs of Staff Army Martin Dempsey have been in constant touch with their fellow ministers and chiefs of defense in NATO, Russia and Ukraine.

The secretary attended a NATO defense ministers conference last week in Brussels. While there, he took a few hours to meet with the NATO Ukraine Commission and spent time with Ukraine's acting defense minister Oleksandr Oliynykof.

"Across the administration, our efforts have been focused on de- escalating crisis, supporting the new Ukrainian government with economic assistance and reaffirming our commitments to allies in Central and Eastern Europe," Hagel said, adding, "I strongly support the administration's approach to this de-escalation."

Dempsey said he had spoken to his Russian counterpart, General Valery Gerasimov earlier Wednesday. "I urged continued restraint in the days ahead, in order to preserve room for a diplomatic solution," said the general.

Dempsey has also spoken this week with military chiefs in the Baltics and in Central and Eastern Europe. "They seek our assurance for their security," he said.

Tensions between Kiev and Moscow escalated last week, when armed groups seized government and parliament buildings in Ukraine 's Autonomous Republic of Crimea and took control of two airports. Russian flags were raised over the seized buildings.

On March 1, Russia's upper house of the parliament approved President Vladimir Putin's request for using armed forces in Ukraine "in connection with the extraordinary situation and the threat to the lives of citizens of the Russian Federation."

The United States has suspended all military cooperation with Russia, calling off planned exercises, training and exchanges. Endite