LONDON – It was a warning meant to remind Ecuador that Britain’s patience has limits. But as the stalemate over Julian Assange settled in Friday, it appeared London’s veiled threat that it could storm Ecuador’s embassy and drag Assange out has backfired — drawing supporters to the mission where the WikiLeaks founder is holed up and prompting angry denunciations from Ecuador and elsewhere.

Experts and ex-diplomats say Britain’s Foreign Office, which warned Ecuador of a little-known law that would allow it to sidestep usual diplomatic protocols, messed up by issuing a threat it couldn’t back up.

“It was a big mistake,” said former British ambassador Oliver Miles. “It puts the British government in the position of asking for something illegitimate.”

Britain’s warning was carried in a set of notes delivered to Ecuadorean diplomats Wednesday as they tried to negotiate an agreement over Assange, who has spent nearly two months at the Latin American nation’s London mission in a bid to avoid extradition to Sweden, where he’s wanted over allegations of sexual assault.

The notes, published by Britain on Thursday, said ominously: “You should be aware that there is a legal basis in the U.K. — the Diplomatic and Consular Premises Act — which would allow us to take action to arrest Mr. Assange in the current premises of the embassy.”

Britain passed the law in 1987, after a deadly shooting in 1984 in which a Libyan diplomat opened fire from within his country’s London embassy, killing a British police officer.

The Ecuadoreans were outraged by the notes, accusing Britain of threatening to assault their embassy and calling a crisis meeting of the Union of South American Nations.

Britain’s Foreign Office insists its missive was “not a threat,” something that Miles dismissed with a laugh. “If I tell you, ‘I’m not threatening you but I DO have a very large stick here,’ it’s a question of semantics,” he said.