SAN JOSE DEL CABO, Mexico — President Barack Obama and Russian President Vladimir Putin need one another, an uncomfortable truth for the superpower leader waging a tough re-election campaign and the newly elected Russian leader who is deeply suspicious of the United States.

The two men will use their meeting today, the first since Putin returned to Russia’s top job, to claim leverage. Much of the rest of the Group of 20 economic meeting will be devoted to the European fiscal crisis and the fate of Greece as a part of the euro zone.

“I expect that it will be a candid discussion, it will get down to business,” White House deputy national security adviser Ben Rhodes said ahead of the lengthy morning meeting between Obama and Putin.

“We’ll be able to sustain cooperation in some areas, we’ll have differences in other areas, and we’ll work to try to bridge those differences.”

The G-20 gathering is a natural forum for sideline discussions of the urgent crisis in Syria as well as diplomatic efforts to head off a confrontation with Iran. Russia is a linchpin in world efforts to resolve both crises, and to U.S. goals for the smooth shutdown of the war in Afghanistan. In the longer term, Obama wants Russia’s continued cooperation in nuclear disarmament and nonproliferation.

Obama made a special project of Russia in his first term and arguably needs Moscow’s help even more if he wins a second one. He is trying to avoid a distracting public spat with Russia during this election year, as suggested by an overheard remark to outgoing Russian President Dmitry Medvedev in March. Obama told Medvedev he would have more flexibility to answer Russian complaints about a U.S.-built missile defense shield in Europe after the November election.

Things got off to a rocky start with Putin, when Obama pointedly withheld a customary congratulatory phone call to Putin until days after his May election. Putin appeared to snub Obama by skipping the smaller and weightier Group of Eight meeting that Obama hosted later that month at Camp David, and a planned Oval Office welcome for the new Russian leader.