The pageantry-filled ceremony, officially the State Opening of Parliament but more commonly known as the Queen's Speech, is an outline of the government's policy proposal read by Queen Elizabeth II.
It had been scheduled for June 19 and has been in the queen's diary since April.
A spokesman for British Prime Minister Theresa May refused to confirm the date at a daily briefing, saying only that there would be a statement regarding the Queen's Speech "in due course".
The spokesman added that any update would come from Andrea Leadsom, the government's new representative in the House of Commons.
Conservative leader May lost her parliamentary majority in the election, and ministers have said the government will have to jettison key parts of its manifesto ahead of the Queen's Speech.
May is trying to strike a deal with Northern Ireland's Democratic Unionist Party to have the support of its 10 MPs in parliament.
The speech is normally followed by days of debate and then a vote on the government's programme, which would in effect be a vote of confidence in the government.
"We are working with the DUP in order to reach a deal that will allow the safe passage of the Queen's Speech," May's spokesman said.
The State Opening involves the queen reading out the government's policy plans from a calfskin parchment in an annual tradition dating back to the Middle Ages.
The monarch is clad in white and usually arrives in a gilded carriage with dozens of horsemen to the sounds of the national anthem, "God Save The Queen".
In a bizarre custom dating back to times of hostility between parliament and monarchy, an MP is "held hostage" at Buckingham Palace until she returns safely.
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