U.S. Defense Secretary Chuck Hagel says the United States is stepping up measures to support its European allies during the crisis in Ukraine's Crimea peninsula.

Hagel said the United States is increasing joint training through the U.S. aviation detachment in Poland, and augmenting U.S. participation in NATO's air policing on the Baltic peninsula. NATO has announced that it is stepping up its cooperation with Ukraine amid the crisis.

Hagel added the U.S. administration will remain focused on de-escalating the crisis, supporting the Ukraine government economically and reaffirming commitments to allies in the region during this "defining moment."

"The events of the past week underscore the need for America's continued global engagement and leadership. The President's defense budget reflects that reality, and it helps sustain our commitments and our leadership at a very defining moment."

The administration has announced a $1 billion economic aid package to Ukraine to help stabilize its economy and support elections set for later this year.

Hagel called the aid package "particularly important" along with diplomatic efforts to peacefully resolve the crisis.

The defense secretary also said the United States has suspended all military-to-military cooperation with Russia. Earlier this week, Hagel canceled two previously scheduled trilateral military exercises, one with Russia and Canada, and the other with Russia and Norway.

In an interview with Voice of America Wednesday, U.S. Ambassador to the United Nations Samantha Power warned that if Russia does not "take the off ramp" and de-escalate the crisis in the Ukraine, the U.S. is prepared to retaliate, canceling trade engagements and looking into targeted sanctions for those deemed responsible for what she called "this act of aggression."

"It's really, really important that Russia takes the hand that's been extended and engages peacefully rather than through military means or this could escalate in a hurry."

Power also encouraged Russia to embrace international monitors in Crimea as a way to get out of the crisis.