NATO's top commander and head of the US European Command, General Philip Breedlove, also planned to confer with Central and Eastern European defense chiefs, Hagel said.
"This is a time for wise, steady, and firm leadership," Hagel told the Senate Armed Services Committee.
"It is a time for all of us to stand with the Ukrainian people in support of their territorial integrity and sovereignty, and their right to have a government that fulfills the aspirations of its people."
At the same hearing, General Martin Dempsey, the US military's top-ranking officer, said he had spoken to his Russian counterpart, General Valery Gerasimov earlier Wednesday, urging "restraint."
"I conveyed to him the degree to which Russia’s territorial aggression has been repudiated globally. I urged continued restraint in the days ahead, in order to preserve room for a diplomatic solution," the general said.
Dempsey, chairman of the US Joint Chiefs of Staff, said he had also spoken this week to military chiefs in the Baltics and in Central and Eastern Europe.
"Understandably, they are concerned. They seek our assurance for their security," he said.