“This continued delinkage is going to be put to the test,” said Samuel Charap, a senior fellow at the International Institute for Strategic Studies. “It’s not going to be as politically possible.”

Though the list of bilateral projects is thinner than it was four years ago, Russia is in the position to provide Mr. Obama with something fundamental to his desired legacy: a deep second round of nuclear cuts. United States negotiators argue that Russia has an interest in trimming its aging stockpile, in part because it is investing trillions of rubles in modernizing its nuclear forces.

So far, the Russian side has said it will discuss cuts only if it has a guarantee that a planned European missile defense system would not be so extensive as to eliminate Moscow’s nuclear deterrent. But Mr. Charap, who recently left the State Department, said Russian language had been softening.

“I think they are waiting for us to put something on the table,” he said. “And waiting for the boss to opine.”

Mr. Putin has asked for a personal meeting with Mr. Obama, and in a telephone conversation on Tuesday, Mr. Obama accepted his invitation to visit Russia, the Kremlin announced. It will be the third meeting between the two, and — at least for Mr. Putin — a pivotal one. Their relationship got off to a sour start in 2009, when Mr. Obama publicly praised Mr. Medvedev at Mr. Putin’s expense, saying Mr. Putin “has one foot in the old ways of doing business and one foot in the new.” In May, Mr. Putin stayed home from the Group of 8 summit meeting, which Mr. Obama had promoted as an opportunity “to spend time” with the Russian leader.

Mr. Putin was said to be disappointed by the Western reaction to his decision to return to the presidency last year, and by Washington’s criticism of Russia’s handling of antigovernment protests, which was seen, an official said, “not to be very loyal.” But analysts say he has a healthy respect for Mr. Obama, in part because of what happened at their first meeting: Mr. Obama listened quietly to his litany of complaints about United States policy and went on to overhaul missile defense plans in Europe, said Dmitri V. Trenin, director of the Carnegie Moscow Center.