WASHINGTON (AP) -- Since the Cold War ended two decades ago, Washington has considered Moscow mostly as an unreliable ally -- and, at times, a stubborn adversary, in efforts to boost the global economy, curb weapons proliferation and calm other nations in tumult. At the same time, Russia's role as a key participant in international efforts to solve global crises gives it the ability to hurt the U.S. if it decides to be uncooperative or openly obstructive.
Some of the tensions can be chalked up to pure competition. The range and scope of Russia's natural resources are second only to the U.S. and it is the world's largest natural-gas exporter. Moscow has stepped up diplomatic ties with China and, more recently, across the Mideast to provide a counterpoint to Western influences in countries the U.S. is trying to win over. This week, President Barack Obama downplayed Russia as a "regional power" -- despite Russian President Vladimir Putin's clear desire to restore his country to the global superpower status it held as the core of the Soviet Union.
The monthlong crisis in Ukraine that led to Russia annexing the strategic Crimean Peninsula has forged a new bitterness between Moscow and Washington. It's too soon to say whether relations will fully freeze over, especially in areas where both sides share a common interest. But, "given Putin shows no signs of backing down here," former Obama administration national security adviser Tom Donilon said earlier this month, "I think we're in for a very difficult time in Russia-U.S. relations."
Some key areas where the U.S. and Russia are still working together -- for now.
Both Russia and the U.S. have been clear about wanting to limit Iran's ability to build a nuclear bomb. At last week's negotiations session in Vienna between world powers and Iran, officials said U.S. and Russian diplomats openly agreed to ignore other topics and together focus on the talks with Tehran.
Iran often sought to exploit U.S.-Russian differences in the past and it may use the current tensions to resist significant nuclear cutbacks. Moscow already has an agreeable relationship with Tehran: Russia is one of Iran's main trading partners and has sold Iran arms over the years. Russia built Iran's first nuclear reactor and is drafting an agreement to build two more.
Russian Deputy Foreign Minister Sergei Ryabkov warned last week that Moscow wouldn't like to use the negotiations with Iran as "an element of the game of raising the stakes" with the West amid tensions over Ukraine. But he added that, "if they force us into that, we will take retaliatory measures."
However, the U.S. has developed much of the negotiation strategy against Iran. Harsh U.S. and European Union sanctions against oil exports and threat of U.S. or Israeli military action has, says former U.S. Ambassador James F. Jeffrey, largely been the driving force behind Iran's willingness to negotiate. "These tools remain with or without Russian cooperation," says Jeffrey, a fellow at the Washington Institute for Near East Policy.
Russia and the U.S. have been at odds over Syria, where Washington and the West want to see opposition forces succeed in their three-year battle against Syrian President Bashar Assad, who has Moscow's support. Russia has sold weapons to Syria's military and repeatedly blocked United Nations resolutions to condemn or sanction Assad's government. If Russia chooses to play a spoiler on Syria, it may boost financial aid and weapons supplies to Assad.
However, Russia has agreed to help broker a cease-fire and a transitional government, and over the last year has worked with the U.S. to bring Assad officials and rebel leaders to negotiate. But those efforts have failed to yield any breakthroughs. Russia is also vital in leaning on Assad's government to give up its chemical weapons stockpile -- less than half of which has been shipped out against a June 30 deadline.
"It's not that we need something from Russia -- it's that the Syrian people need the Russians and the Iranians and anyone else with influence over the regime to keep pushing them," State Department deputy spokeswoman Marie Harf said Wednesday. "Quite frankly, we have been able to work together on Syria, on things like chemical weapons, even when we very strongly disagree with other parts of their Syria policy, certainly."
Russia has played a key role in providing air and land corridors for supplying the U.S. and other coalition troops in Afghanistan. It has provided an alternative to a route through Pakistan, which has been unstable amid local protests.