LONDON // An American soldier's killing spree in Afghanistan likely will be high on the agenda when David Cameron, the UK prime minister, arrives in the United States today for a summit with the nation's president, Barack Obama.
The two already had plenty to discuss: the bloodshed in Syria, as well as Iran's nuclear facilities and Israel's threats to attack them.
The killings in Afghanistan have "thrown a spanner into works that were already creaking badly", said one diplomat in London yesterday.
"Both leaders are determined to withdraw from active military operations by 2014, and they had been hoping to do it with as little fuss as possible," he said. "But the Quran burnings and this massacre have the potential to lose the allies what little goodwill they had managed to create among ordinary people.
"The two will also, no doubt, try to come up with something positive to say about reconciliation in Afghanistan post-2014, but it is hard to avoid an all-pervading gloom on both sides of the Atlantic about the country's immediate future."
A US soldier killed 16 villagers in southern Afghanistan on Sunday, and Douglas Alexander, Britain's opposition foreign secretary, emphasised yesterday the additional risks international forces now face.
"That is why there needs to be a renewed diplomatic effort to try to find a negotiated solution to this conflict," he said in a BBC radio interview.
"But the window of opportunity for that negotiated settlement is rapidly diminishing, which is why I welcome the fact that the prime minister is going to Washington. I hope that Afghanistan will be at the top of the international agenda."
It will be Iran, though, that could prove the most intractable problem for the two leaders. Neither wants to see the development of a nuclear arsenal in the Gulf or an Israeli military strike against it.
Last week, Mr Obama suggested there was still a window of opportunity to peacefully resolve the problems over Tehran's nuclear programme. The suggestion was welcomed by Ayatollah Ali Khamenei, Iran's supreme leader, "perhaps offering an opportunity for Obama and Cameron to explore ideas for coming up with something new", said the diplomat.
Little is expected to be achieved on Syria during the Washington talks.
Away from pressing global concerns, Mr Cameron's visit is expected to cement the close professional relationship he has with Mr Obama - and the more personal one that exists between their wives, Samantha and Michelle.
Tonight, Mr Cameron and Mr Obama will fly together in Air Force One as the two men head to Dayton, Ohio, to attend a college basketball game. Ohio is a key state in November's presidential election.
During the halftime break, the men will give their only joint interview of the trip, to a sportscaster.