Environment ministers are in the Argentine capital, Buenos Aires, in an effort to overcome serious differences over tackling global warming.
Mr Biden told the conference it was "no secret" that Moscow and Washington had "serious differences" on issues such as Syria.
Nawaz Sharif's removal from active politics and banishment to Saudi Arabia also led to serious differences emerging within his Pakistan Muslim League (PML) party.
"There is no question that serious differences remain, " Clinton told reporters.
Memos leaked earlier this year suggest there are serious differences among Vatican officials over how far to go in ensuring financial transparency, according to media reports.
The most serious differences between the bills surround the recourse patients have if they are denied coverage by their HMO and are harmed by delays in treatment.
PFI, the tension that is building between him and Mr Blair over public-service reform is potentially far more serious than their previous differences over the euro.
French officials seem unable to accept that such differences might be serious.
He wanted to show that there were differences, and they were serious.
It will take a serious and sustained effort to resolve the many differences between Iran and the United States.
Even during the campaign they have stuck to an unwritten code, freely expressing differences but carefully avoiding any escalation into serious conflict.
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