"Administrator Bolden made it clear in his answers that the Obama Administration has no contingency plan in place to send U.S. astronauts to the International Space Station if Russia chooses to end the current agreement that allows our astronauts to travel to the space station on board its Soyuz capsules."
NASA's chief confirms it: Without Russia, space station lost, Houston Chronicle
'If Russia stops flying U.S. astronauts to the International Space Station, the U.S., lacking a backup plan, would have no choice but to abandon the multibillion dollar outpost to its own fate, NASA Administrator Charles Bolden said Wednesday. "We would make an orderly evacuation," Bolden said during a U.S. House Appropriations subcommittee hearing."
Keith's note: Culberson is not exaggerating. When asked, Bolden could not give a 'yes' or 'no' answer to rather specific and repeated questions as to whether or not NASA has a post-Russia ISS contingency plan in place. Bolden stumbled for a bit before he started to talk about an orderly evacuation of the ISS. Culberson interrupted at one point and said "please tell me that you do". Bolden also seemed to suggest that the U.S. can operate the ISS without Russian permission/cooperation.