Argentina's ambassador to London has declined an invitation to attend the funeral of Margaret Thatcher, Downing Street said today.
o 10 invited Alicia Castro to tomorrow's proceedings but did not extend an invitation to President Cristina Fernandez de Kirchner
The Prime Minister's official spokesman said the decision to refuse was a "matter for the Argentine ambassador".
It comes amid increased attention on the international guestlist for the ceremony, particularly attendees from the United States.
Downing Street insisted that David Cameron was not disappointed with Washington's decision not to send currently serving senior politicians to the ceremonial funeral.
Barack Obama's official presidential delegation will be led by George Shultz and James Baker, who both served as secretaries of state during the Thatcher era.
Former US vice-president Dick Cheney and ex-secretary of state Henry Kissinger are also due to attend the funeral at St Paul's Cathedral.
The Prime Minister's official spokesman said: "I think the fact that the official US delegation includes two former secretaries of state with whom she had a very close personal working relationship is testament to the esteem with which she was held."
Also on the list of attendees announced today are Crown Prince Pavlos and Princess Marie-Chantal of Greece, two-time US presidential candidate Ross Perot and Olympics supremo Lord Coe.
Asked about security at the event in light of the Boston terror attack No 10 said arrangements for major events "are permanently kept under review as a matter of course".
The former prime minister's coffin will lie in Parliament's Chapel of St Mary Undercroft.
A private service for Lady Thatcher will be held at the chapel attended by her family and senior figures from both Houses of Parliament.
The spokesman said he was "not aware" of plans for Mr Cameron to attend tonight.
The body of Margaret Thatcher, who died last week aged 87, will make its final journey to Parliament today ahead of a potentially bitter debate in the Commons about her legacy.
The debate was triggered by outspoken Respect MP George Galloway who, along with Labour veteran Dennis Skinner, objected last night to a business motion which would see tomorrow's session of Prime Minister's Questions cancelled so that Mr Cameron and MPs can attend the funeral service.
The pair's cry of "object" means the proposed change in sitting time will now be voted on after a debate lasting up to three hours this evening.
Mr Galloway said: "This was a wicked and divisive woman who was hated by half of the country and did great damage to a society she said didn't exist.
"People think the canonisation of Lady Thatcher has gone on long enough. The muffling of the chimes of Big Ben is a step too far and now Mr Cameron will miss Prime Minister's Questions for four weeks. It is unconscionable."
After tonight's service in the Chapel of St Mary Undercroft the Speaker's Chaplain, the Rev Rose Hudson-Wilkin, will maintain a vigil through the night.
Thatcher's coffin will leave the Palace of Westminster by hearse tomorrow before being transferred to a gun carriage for the final leg of its journey to St Paul's.