The Cold War is over, though given the increasingly heated exchanges of late, it's hard to tell.
For decades, Moscow and Washington went at it -- diplomatically, militarily, economically, you name it -- until the 1991 fall of the Soviet Union changed the equation. Yet anyone following officials biting back-and-forth in recent days on what to do in Syria could reasonably surmise the two world powers are at it again.
What this means for what unfolds in Syria, for relations between the two nations, and for world politics generally remains to be seen. Yet a look back at comments since Vladimir Putin returned for a second stint as Russia's president, and particularly as the barbs have grown testy over the past few weeks, suggests the two sides have grown even further apart.
'I don't have a bad personal relationship with Putin'
President Barack Obama said as much in August, referring to his relationship with Russia's powerful leader.
At the same time, he acknowledged, "anti-American" rhetoric has ramped up since Putin returned to the presidency in May 2012. And, Obama added, he'd had "mixed success" trying to get "Putin to think forward, as opposed to backwards" on some issues.
Things appeared to go differently when Dmitry Medvedev was president. (At that time, Putin had become prime minister after serving his first eight years as president.) Medvedev and Obama scored significant agreements on arms control and letting NATO troops get to Afghanistan through Russia.
Yet the atmosphere changed noticeably after Putin, a former KGB operative, resumed the top position in Russia's government. There were diplomatic flare-ups on everything from espionage to human rights to the adoption of Russian children.
One point of strain has, in many ways, the potential to have the biggest global impact: what to do about a civil war in Syria that has left more than 100,000 dead and 2 million refugees, especially given allegations from both sides about chemical weapons use.
'Obama hasn't been elected ... to be pleasant to Russia'
Putin made this comment earlier this week, before Obama and other leaders arrived in St. Petersburg, Russia, for the G20 summit.
His point, it seemed, was that the chief goal of neither he nor Obama is to ingratiate themselves to each other or please each others' citizens. Both men were elected to serve their own populaces, and if they end up throwing some elbows along the way -- well, that's how things go.
Not that the two can't make nice. Obama said their conversations are often candid and "very productive." And when they met Thursday before reporters in St. Petersburg, the two men smiled as they chatted and shook hands.
But none of that changes the fact that on the big issue of the day -- Syria -- the two are far apart.
Moscow and Washington have been at odds since 2011, when the Damascus government first cracked down on protesters. Since then, the dispute has spiraled into a full-fledged civil war pitting Syrian government forces (who, at times, have lost control over large tracts of territory) against an opposition fighting force that ranges from moderates to Islamist extremists.
Sure, both Russia -- a longtime ally of Syria and its president, Bashar al-Assad -- and the United States have been part of international efforts to forge cease-fires or a political solution. But all such attempts have failed.
'My credibility isn't on the line -- the international community's credibility is'
The issue of chemical weapons has raised the stakes, and the tensions.
In April, U.S. Defense Secretary Chuck Hagel accused al-Assad's government of being behind small-scale, but still deadly use of the nerve agent sarin. The French foreign minister made similar accusations in June.
An August 21 attack just outside Damascus put the matter front-and-center on the world stage. Within days, U.S. officials -- including Secretary of State John Kerry, who said Sunday that blood and hair samples from the scene "tested positive for signatures of sarin" gas -- blamed al-Assad's forces for an attack they estimated had killed more than 1,400 people, many of them children.
Putin and other Russian officials, however, have been skeptical of such claims from the United States, Britain and France. Russia's president said Wednesday it would be "absurd" for al-Assad -- whose government has firmly denied using chemical weapons and accused "terrorists," its blanket term for rebel fighters, of doing so -- to wage such an attack when he's gaining an upper hand.
(In fact, that same day, Russia's foreign ministry announced that its experts determined a "homemade" device that Syria's army does not possess was used in a chemical attack in March. The projectile, the ministry stated, was similar to those used in northern Syria by Bashaar Al-Nasr, an Islamist brigade that is part of the opposition Syria Liberation Front.)
Yet despite fierce resistance -- even reliable U.S. ally Britain won't join in any military intervention, following a vote by Parliament -- Obama has pressed on. Calling the Syrian attack a "challenge to the world," the 2009 Nobel Peace Prize winner has said action is necessary to enforce international chemical weapons bans.
His comment on "the international community's credibility" on Wednesday, while standing alongside Swedish Prime Minister Fredrik Reinfeldt, reflects his argument that the unfolding debate is not about whether he should live up to his 2012 comment that use of chemical weapons in Syria crosses a "red line" that must be responded to militarily.
Rather, he contended, the entire world -- not just the United States -- has an obligation to respond.