In a surprise accord, Ukraine and Russia agreed Thursday on tentative steps to halt violence and calm tensions along their shared border after more than a month of Cold War-style military posturing triggered by Moscow's annexation of Crimea. Russia's pledge to refrain from further provocative actions drew support but also a measure of skepticism from President Obama, who said at a news conference at the White House that the United States and its allies were prepared to ratchet up sanctions if Moscow doesn't fulfill its commitments. The aid will include medical supplies, helmets, water purification units and power generators.