WASHINGTON — When he arrived in Moscow for national security talks Monday, President Obama was tracing the footsteps of U.S. presidents dating back to Eisenhower. And, like many of his predecessors, Obama found out what difficult bargaining partners the Russians can make.
The two sides took small steps toward scaling back their nuclear arsenals but left wide differences and lingering difficulties on other issues, such as Iran, missile defense, American military support to Russia's neighbors and human rights.
"I don't want to use the word 'disappointment,' but clearly there's a long way to go to work out an agreement, and to move U.S.-Russian relations to more solid ground," said John D. Isaacs, president of the Council for a Livable World, an arms control advocacy group.
Although Russia bears little resemblance today to America's onetime chief rival and peer superpower, Obama has the best of reasons for the respectful approach he has chosen for dealing with the new lords of the Kremlin: They can block the path to nearly every one of his foreign policy priorities.
In its role as spoiler, Russia has the leverage to undermine U.S. efforts to contain Iran's nuclear program, to stop extremism in Afghanistan, to broker Middle East peace and to halt the spread of nuclear weapons.
"They have an enormous ability to create problems if they don't think their interests are taken into account," said Paul J. Saunders, a State Department official in President George W. Bush's administration.
Moscow's differences with Washington were on display in Obama's first summit with President Dmitry Medvedev. On most of the key issues, the two could agree only to keep talking.
The leverage over the United States comes from various sources, including Russia's historical ties with other countries, its huge energy resources and its geographic location.
Russia's long-standing economic relationship with Iran has been a principal hurdle to American efforts to curb Tehran's nuclear ambitions.
Although the West believes tough sanctions by Moscow would play a decisive role, Russia has continued to balk. At their news conference, Obama cited the threat of Iran obtaining nuclear weapons, but Medvedev remained silent, refraining from even mentioning Iran by name.
Russia has been uneasy about the U.S. military presence in Central Asia and has posed a threat to American efforts to keep open military supply lines to Afghanistan, playing a role in Kyrgyzstan's decision this year, later reversed, to deny the U.S. access to one of its bases.
On Monday, Moscow shifted position on Afghanistan, approving as many as 10 U.S. flights a day through Russian airspace.
That decision, along with another to resume military contacts that were cut off last year after the clash between Russia and Georgia, were among the few bright spots from the summit.
But Russian cooperation is not a given in other U.S. diplomatic pursuits.
Moscow voted in favor of recent United Nations sanctions aimed at punishing North Korea for its second nuclear test, conducted in May. Yet it remains to be seen whether Russia will follow through on the sanctions, which call for countries to try to block North Korea's sea and air shipments of suspected banned weapons.
Russia has only a limited ability to push the principal players in the Arab-Israeli dispute toward peace. Yet, a displeased Moscow has the power to threaten the effort, for instance, by selling Arab states such as Syria high-tech weaponry that could destabilize the region.
"They don't have the ability to create a positive outcome, but they do have leverage on the negative side," said Saunders, now executive director of the Nixon Center, a think tank.
Some of the festering disagreements between the two countries were shelved. The two presidents agreed to jointly study Iran, and to look again at the question of a proposed U.S. missile defense system in Eastern Europe, which Russia views as a threat to its security.
On arms control, the marquee issue of the summit, Russian officials as well as American officials of both political parties favor cuts. But this week's meetings have again proved that it's an elusive goal.
The two sides announced that they have reached preliminary agreement on a follow-up to the Strategic Arms Reduction Treaty, but the deal is unlikely to be completed by Dec. 5, when the current agreement expires.
And the target reductions are far less than many had hoped for.
Charles D. Ferguson, a scientist at the Council on Foreign Relations, a think tank, noted that the new agreement would cut the maximum number of warheads to between 1,500 and 1,675 for each side. That is only slightly less than the 1,700 to 2,200 allowed under the current treaty.
Ferguson also noted that the new pact would set a limit of between 500 and 1,100 devices that can deliver the warheads, down from the ceiling of 1,600. But the Russians have only about 800 delivery systems.
"This is incremental," Ferguson said. "When you pull back the curtain, the wizard reveals that we're almost pretty much there."