MOSCOW — A White House official says he expects President Barack Obama and Russian President Dmitry Medvedev to announce a deal Monday that could lead to a new nuclear arms reduction treaty by year's end.

Gary Samore — Obama's top adviser on arms control — would not give specifics about the agreement. But he says he expects the two presidents to announce that progress had been made and that negotiations would continue.

Obama arrives in Moscow on Monday for two days of meetings. Samore spoke to reporters in Moscow ahead of Obama's arrival.