"On the advice of Mr Assange's legal counsel, today's planned announcement by Mr Assange from the balcony of the Ecuadorian embassy has been deferred.
"This follows the agreement of an imminent meeting with British authorities," WikiLeaks said in a statement.
Assange's planned appearance at the embassy balcony was due to mark five years since he took refuge in the Ecuadorian territory within London, in a bid to avoid extradition to Sweden where he faced allegations of rape.
Assange declared "victory" following the announcement, although he declined to say whether he would step out onto British soil where he could be arrested for earlier skipping bail.
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Today, WikiLeaks said Assange's legal team "remain optimistic" of finding a solution "which respects the British legal process and restores Mr. Assange's freedom and dignity".
The British government denied it had any plans to meet with Assange, despite the claim made by WikiLeaks.
Assange said he opted to move into the Ecuadorian embassy to avoid being extradited to the US where he fears prosecution over WikiLeaks publishing leaked government documents.
US justice authorities have never confirmed that they have Assange under investigation or are seeking his extradition.
But US Attorney General Jeff Sessions said last month that "we will seek to put some people in jail", when asked if arresting Assange was a "priority" for Washington.