WASHINGTON, March 3 - Russian President Vladimir Putin needs to allow international monitors to mediate a deal in Ukraine acceptable to all Ukrainian people, US President Barack Obama said Monday, Reuters reported.

The U.S. is weighing its response to Russia's so far bloodless incursion into Crimea. Despite an international outcry, Putin has shown little sign of backing down, and Russia has built up armored vehicle presence near Crimea and staged military maneuvers in what appears to be a show of strength.