The Organization of American States on Friday called a meeting of foreign ministers for August 24 to discuss the standoff sparked when Ecuador gave asylum to WikiLeaks founder Julian Assange.
Twenty-three countries voted for the resolution proposed by Ecuador to convene the meeting at its Washington headquarters to discuss Quito's standoff with Britain over Assange.
The vote was taken at emergency talks to discuss the Assange case.
The United States, Canada and Trinidad and Tobago voted no. Five countries abstained, and three others were absent.
Assange, a 41-year-old Australian national, took refuge at Ecuador's embassy in London on June 19 to avoid extradition to Sweden, where he is wanted for questioning over alleged sexual misconduct.
Ecuador granted political asylum to Assange on Thursday, triggering a diplomatic row with London, which angrily insisted it would still move to extradite him.
Assange supporters fear Sweden could eventually send him to the United States, where he could face charges over his website's publication of a trove of classified US documents, some about the wars in Afghanistan and Iraq.
The US envoy to the OAS, Carmen Lomellin, said a meeting of OAS foreign ministers "would be unhelpful and harmful to the OAS' reputation as an institution."
Ecuador wants the body to discuss what it says was a threat by Britain to storm its embassy by force to take Assange into custody.
But Philip Barton, Britain's envoy to the OAS as an observer, said: "Allegations that the UK was threatening Ecuador and about to storm the embassy are without foundation."
London has said it could invoke the Diplomatic and Consular Premises Act of 1987, which it says allows it to revoke the diplomatic immunity of an embassy on British soil.
Under a 1954 agreement, the OAS agreed to allow asylum in diplomatic missions for "persons being sought for political reasons," although not individuals indicted for "common offenses."
The United States said earlier Friday it does not believe in the concept of "diplomatic asylum."
"We believe this is a bilateral issue between Ecuador and the United Kingdom and that the OAS has no role to play in this matter," the State Department said in a statement.