The U.S. began sending Meals Ready to Eat to Ukraine but the urgent requests from Kiev for weapons, medical supplies and other military assistance remain on hold.
The U.S. European Command was in the process of sending 25,000 cases of the rations to the Ukrainian city of Yavoriv. The MREs should arrive before the end of the week, said Rear Adm. John Kirby, the Pentagon press secretary.
Defense Secretary Chuck Hagel was still reviewing Ukraine's request for other military aid and there was no timeline on a decision, Kirby said at a Pentagon briefing.
Several members of Congress from both parties have called on the Obama administration to approve sending small arms and communications gear to Ukraine.
Russian troops backed by tanks and artillery were on the eastern borders of Ukraine for what Moscow has called "spring exercises" following the annexation of Crimea by President Vladimir Putin.
"They continue to have forces amassed to the east and south of Ukraine," said Kirby. He declined to give an estimate on the size of the force but said "they certainly have the capability, if they want, to cross into Ukraine."
The crisis in Ukraine was the main topic of President Obama's meetings in Belgium with European leaders, China and Japan as members of the G-7 group of major Western economies.
After a two-hour closed meeting, the leaders voted to exclude Putting from what would have been a G-8 meeting and also canceled a planned G-8 meeting in June in Sochi, the Russian site of the Winter Olympics.
"This group came together because of shared beliefs and shared responsibilities. Russia's actions in recent weeks are not consistent with them," the leaders said in a statement referring to the takeover of Crimea.
"Under these circumstances, we will not participate in the planned Sochi Summit. We will suspend our participation in the G-8 until Russia changes course," the statement said.
The leaders said the cancellation of the Sochi summit should be seen as the first step in an escalating series of political and economic moves aimed at punishing Russia if Putin fails to change course.
"We remain ready to intensify actions including coordinated sectoral sanctions that will have an increasingly significant impact on the Russian economy, if Russia continues to escalate this situation," the leaders' statement said.
Earlier, Obama said "we're united in imposing a cost on Russia for its actions so far."
"The growing sanctions would bring significant consequences to the Russian economy," Obama said.
-- Richard Sisk can be reached at firstname.lastname@example.org