Thatcher, Britain's first woman and longest serving prime minister of the 20th century, died Monday aged 87 after suffering a stroke. She had suffered dementia for more than a decade.
Downing Street said over 2,000 invitations will be sent out to people of various circles including cultural and press figures, Xinhua reported.
People on the list include all surviving former prime ministers of Britain and former US presidents, along with former US secretary Hillary Clinton.
The Queen and Duke of Edinburgh have already been confirmed for the ceremony.
Family, friends, colleagues and aides of Thatcher during her time in power have all been invited to the ceremony, where she will also be given full military honours.
Current cabinet members and Labour leader Ed Miliband are also invited.
Thatcher's funeral will take place at St Paul's Cathedral in London April 17.
It will be the first funeral of a British politician attended by the Queen since that of Sir Winston Churchill in 1965.
Over 700 armed forces personnel will line the route of the funeral procession from Westminster to St Paul's, including three bands whose drums will be covered in black cloth, BBC reported.
A gun salute will be fired from the Tower of London. The coffin will be carried into St Paul's by service personnel from regiments and ships closely associated with the Falklands campaign.
Security for the funeral is likely to be extremely tight with fears of disruption by Irish republican dissidents and far-left groups, according to local media.
Concerns about potential violence rose after trouble erupted at several street parties celebrating her death Monday night in London, Liverpool, Bristol and Glasgow.