Five years ago, US President George W. Bush and Russian President Vladimir Putin hit it off so well in their first meeting that Bush famously said he trusted Putin after getting "a sense of his soul."
But at next weekend's Group of Eight summit in St. Petersburg, tensions between the two world leaders will be unmistakable even though both will try to play down the rift.
The Russian president has grown annoyed with Washington's accusations that he is restricting freedoms and with a push to expand the Nato alliance further into his neighbourhood.
Bush has been frustrated by Russia's resistance to a tougher line on Iran's nuclear ambitions and its Iraq war opposition.
"The relationship is not what it was four and a half years ago. Each leader views the other with more suspicion," said James Goldgeier, a professor at George Washington University.
As Putin prepares to host the July 15-17 G8 summit in his hometown of St. Petersburg, the event's choreography will emphasise co-operation and camaraderie.
"I expect the summit to go pretty much as scripted," said Sarah Mendelson of the Center for Strategic and International Studies. "This is a big moment for Putin."
But Mendelson said there are serious differences that many observers worry could get worse.
Bush told the CNN talk show "Larry King Live" he hoped for candor in his talks with Putin and promised not to lecture him.
The two will dine together on Friday and hold talks the next day before the summit opens. US officials said it was a good bet that Bush would remind Putin of concerns about his record on democracy.
Putin wants to keep the summit's focus on energy security, highlighting Russia's growing clout as an energy supplier.
CIVILIAN NUCLEAR COOPERATION:
More broadly, a partnership between the former Cold War rivals is important to both Putin and Bush. A US-Russian deal to start civilian nuclear co-operation talks, which the Washington Post says will be formally unveiled at the G8 summit, could help them emphasise that.
But neither leader has an interest in completely glossing over the disagreements.
Bush was criticised as naive by some Democrats as well as Republicans when he talked of peering into Putin's soul.
Lawmakers lately have boosted pressure on Bush to complain about such steps as Russian restrictions on civil society groups and greater state control over broadcast media.
Among the critics is potential 2008 presidential candidate Sen. John McCain. Earlier this year the Arizona Republican urged Bush to consider boycotting the St. Petersburg summit to protest Russia's democratic record.
Bush is trying to send that message in less drastic ways. Vice President Dick Cheney, during a May tour of ex-communist states, accused Russia of backsliding on democracy and trying to use its energy resources to bully its neighbours.
In a more subtle gesture also likely to have annoyed Moscow, Bush last week welcomed Georgian President Mikhail Saakashvili, a Putin critic, to the White House and praised his commitment to freedom while backing Georgia's desire to join Nato.
Perhaps foreshadowing frictions at the G8, US Secretary of State Condoleeza Rice and Russian Foreign Minister Sergei Lavrov were heard quarrelling about a communique on Iraq last month when aides forgot to turn off a microphone in a closed-door meeting.
Among the top issues at the G8 summit are concerns about North Korea's test-firing of missiles and a push for an Iranian response to an incentives package aimed at getting Tehran to halt its uranium enrichment.
In both cases, Washington would like raise a threat of sanctions as a consequence of defiance by Pyongyang and Tehran. MMoscow is cool to the idea.