WASHINGTON — President Barack Obama moved to tighten sanctions on Syria and Iran on Monday by taking aim at those who provide their authoritarian governments with technology to track down dissidents for abuse, torture or death.

WASHINGTON — For President Barack Obama, this is what bipartisanship looks like in the new era: messy, combustible and painful, brought on under the threat of even more unpalatable consequences and yet still deferring the ultimate resolution for another day.

WASHINGTON — Just two weeks after an election that left him struggling to find his way forward, President Barack Obama has decided to confront Senate Republicans in a make-or-break battle over arms control that could be an early test of his mettle heading into the final two years of his term.

WASHINGTON — Just two weeks after an election that left him struggling to find his way forward, President Barack Obama has decided to confront Senate Republicans in a make-or-break battle over arms control that could be an early test of his mettle heading into the final two years of his term.

WASHINGTON — President Barack Obama’s arms control treaty with Russia advanced to the Senate floor with bipartisan support Thursday, giving it a major boost toward ratification despite the election-year polarization that has divided the parties over so many other issues.

WASHINGTON — President Barack Obama will nominate Solicitor General Elena Kagan as the nation’s 112th justice, choosing his own chief advocate before the Supreme Court to join it in ruling on cases critical to his view of the country’s future, Democrats close to the White House said on Sunday.

With flourish and fanfare, President Barack Obama and President Dmitry A. Medvedev of Russia signed a nuclear arms control treaty on Thursday and opened what they hoped would be a new era in the tumultuous relationship between two former Cold War adversaries.

President Barack Obama sent a secret letter to Russia’s president last month suggesting that he would back off deploying a new missile defense system in Eastern Europe if Moscow would help stop Iran from developing long-range weapons, American officials said Monday.

During almost two years on the campaign trail, Barack Obama vowed to slay the demons of Washington, bar lobbyists from his administration and usher in what he would later call in his Inaugural Address a “new era of responsibility.” What he did not talk much about were the asterisks.

President-elect Barack Obama put the rancor and even some of the rhetoric of the presidential campaign behind him on Monday as he welcomed his chief Democratic adversary into his Cabinet and signaled flexibility in his plans to withdraw troops from Iraq.