Invites to the Queen’s funeral have not been sent to Russia, Belarus and Myanmar, Whitehall sources have told PA.
Iran will only be represented at an ambassadorial level, insiders claim.
Britain has not invited representatives from the three nations to Monday's state funeral as the sovereign is laid to rest with Prince Philip in St George's Chapel.
The UK, along with its Western allies, has sought to isolate Russia and its ally Belarus on the world stage with economic sanctions and other measures in response to Moscow's
invasion of Ukraine.
Myanmar and its military have also been the subject of British sanctions and have not been invited to attend the ceremony, it is reported.
About 500 foreign dignitaries are expected to attend the funeral in London, with invites now sent to the heads of state of most countries with which Britain has diplomatic relations, the BBC said.
A host of world leaders from US President Joe Biden and First Lady Jill Biden, to the prime ministers of Canada, Australia and New Zealand have all confirmed attendance for the event, likely to be one of Britain's largest diplomatic gatherings in years.
Kremlin spokesperson Dmitry Peskov announced on Friday that Russian President Vladimir Putin will not attend the funeral.
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Peskov said that although Russians “respect” the Queen “for her wisdom”, Putin’s attendance at the funeral is not an option - but added a decision will be taken on who will represent the nation at the ceremony.
Princess Anne will accompany the Queen's coffin on a flight from Edinburgh to London, arriving later today.
The cortege will then travel to Buckingham Palace where the oak casket will be met by King Charles, the Queen consort and other members of the royal family.
At 2.22pm on Wednesday, the coffin will be taken on a gun carriage of The King’s Troop Royal Horse Artillery to the Palace of Westminster.
Accompanied by the sound of minute guns fired from Hyde Park by The King’s Troop Royal Horse Artillery, the cortege will make a trip past London landmarks.
It will travel via Queen’s Gardens, The Mall, Horse Guards and Horse Guards Arch, Whitehall, Parliament Street, Parliament Square, and New Palace Yard.
The Queen will lie in state until 6.30am on the day of her state funeral on Monday.