MOSCOW (AP) — Presidents Barack Obama and Dmitry Medvedev confidently committed to a year-end deal to slash nuclear stockpiles by about a third on Monday, but the U.S. leader failed to crack stubborn Kremlin objections to America’s missile defense plans — a major stumbling block to such an agreement. Both men renewed pledges to pull U.S.-Russian relations out of the dismal state into which they had descended during the eight years of the Bush administration. And to that end, they signed a series of agreements and joint statements designed to enliven and quicken contacts on a broad range of issues — including cooperation on Afghanistan, a key Obama foreign policy objective. Obama said the leaders both felt relations had “suffered from a sense of drift. President Medvedev and I are committed to leaving behind the suspicion and rivalry of the past.”