US presidential candidate Mitt Romney hailed Margaret Thatcher as a "tower of strength in the cause of liberty" on Saturday as the former prime minister celebrated her 87th birthday.
Baroness Thatcher marked the occasion by having lunch at Green's Restaurant and Oyster Bar in London's exclusive St James's district with her son Mark and his wife.
Writing on Twitter, Mr Romney - the Republican challenger engaged in a close fight with Democrat Barack Obama for the White House in next month's election - tweeted:
The tweet was predictably met with derision on Twitter, with many users reminding Romney that Thatcher is not the most popular British politician of recent years.
The Republican presidential nominee did receive one note of support from British MEP Dan Hannan, who tweeted:
Baroness Thatcher's premiership was thrust back into the American spotlight this year when Meryl Streep starred in a controversial Hollywood film about her.
It drew criticism from Prime Minister David Cameron and others for concentrating on the peer's failing health - a series of small strokes since leaving office have left her frail and with dementia.
She was not sufficiently well to join the Queen for a lunch with former and serving prime ministers as part of the Diamond Jubilee this summer and previously missed her own 85th birthday party thrown by Cameron at 10 Downing Street.
Her last public appearance was at another birthday party, in September last year, when she helped then defence secretary Liam Fox celebrate his 50th.
A spokesman said she was "doing all right".